What are the default color values for the Holo theme on Android 4.0?

If you want the default colors of Android ICS, you just have to go to your Android SDK and look for this path: platforms\android-15\data\res\values\colors.xml.

Here you go:

<!-- For holo theme -->
    <drawable name="screen_background_holo_light">#fff3f3f3</drawable>
    <drawable name="screen_background_holo_dark">#ff000000</drawable>
    <color name="background_holo_dark">#ff000000</color>
    <color name="background_holo_light">#fff3f3f3</color>
    <color name="bright_foreground_holo_dark">@android:color/background_holo_light</color>
    <color name="bright_foreground_holo_light">@android:color/background_holo_dark</color>
    <color name="bright_foreground_disabled_holo_dark">#ff4c4c4c</color>
    <color name="bright_foreground_disabled_holo_light">#ffb2b2b2</color>
    <color name="bright_foreground_inverse_holo_dark">@android:color/bright_foreground_holo_light</color>
    <color name="bright_foreground_inverse_holo_light">@android:color/bright_foreground_holo_dark</color>
    <color name="dim_foreground_holo_dark">#bebebe</color>
    <color name="dim_foreground_disabled_holo_dark">#80bebebe</color>
    <color name="dim_foreground_inverse_holo_dark">#323232</color>
    <color name="dim_foreground_inverse_disabled_holo_dark">#80323232</color>
    <color name="hint_foreground_holo_dark">#808080</color>
    <color name="dim_foreground_holo_light">#323232</color>
    <color name="dim_foreground_disabled_holo_light">#80323232</color>
    <color name="dim_foreground_inverse_holo_light">#bebebe</color>
    <color name="dim_foreground_inverse_disabled_holo_light">#80bebebe</color>
    <color name="hint_foreground_holo_light">#808080</color>
    <color name="highlighted_text_holo_dark">#6633b5e5</color>
    <color name="highlighted_text_holo_light">#6633b5e5</color>
    <color name="link_text_holo_dark">#5c5cff</color>
    <color name="link_text_holo_light">#0000ee</color>

This for the Background:

<color name="background_holo_dark">#ff000000</color>
<color name="background_holo_light">#fff3f3f3</color>

You won't get the same colors if you look this up in Photoshop etc. because they are set up with Alpha values.

Update for API Level 19:

<resources>
    <drawable name="screen_background_light">#ffffffff</drawable>
    <drawable name="screen_background_dark">#ff000000</drawable>
    <drawable name="status_bar_closed_default_background">#ff000000</drawable>
    <drawable name="status_bar_opened_default_background">#ff000000</drawable>
    <drawable name="notification_item_background_color">#ff111111</drawable>
    <drawable name="notification_item_background_color_pressed">#ff454545</drawable>
    <drawable name="search_bar_default_color">#ff000000</drawable>
    <drawable name="safe_mode_background">#60000000</drawable>
    <!-- Background drawable that can be used for a transparent activity to
         be able to display a dark UI: this darkens its background to make
         a dark (default theme) UI more visible. -->
    <drawable name="screen_background_dark_transparent">#80000000</drawable>
    <!-- Background drawable that can be used for a transparent activity to
         be able to display a light UI: this lightens its background to make
         a light UI more visible. -->
    <drawable name="screen_background_light_transparent">#80ffffff</drawable>
    <color name="safe_mode_text">#80ffffff</color>
    <color name="white">#ffffffff</color>
    <color name="black">#ff000000</color>
    <color name="transparent">#00000000</color>
    <color name="background_dark">#ff000000</color>
    <color name="background_light">#ffffffff</color>
    <color name="bright_foreground_dark">@android:color/background_light</color>
    <color name="bright_foreground_light">@android:color/background_dark</color>
    <color name="bright_foreground_dark_disabled">#80ffffff</color>
    <color name="bright_foreground_light_disabled">#80000000</color>
    <color name="bright_foreground_dark_inverse">@android:color/bright_foreground_light</color>
    <color name="bright_foreground_light_inverse">@android:color/bright_foreground_dark</color>
    <color name="dim_foreground_dark">#bebebe</color>
    <color name="dim_foreground_dark_disabled">#80bebebe</color>
    <color name="dim_foreground_dark_inverse">#323232</color>
    <color name="dim_foreground_dark_inverse_disabled">#80323232</color>
    <color name="hint_foreground_dark">#808080</color>
    <color name="dim_foreground_light">#323232</color>
    <color name="dim_foreground_light_disabled">#80323232</color>
    <color name="dim_foreground_light_inverse">#bebebe</color>
    <color name="dim_foreground_light_inverse_disabled">#80bebebe</color>
    <color name="hint_foreground_light">#808080</color>
    <color name="highlighted_text_dark">#9983CC39</color>
    <color name="highlighted_text_light">#9983CC39</color>
    <color name="link_text_dark">#5c5cff</color>
    <color name="link_text_light">#0000ee</color>
    <color name="suggestion_highlight_text">#177bbd</color>

    <drawable name="stat_notify_sync_noanim">@drawable/stat_notify_sync_anim0</drawable>
    <drawable name="stat_sys_download_done">@drawable/stat_sys_download_done_static</drawable>
    <drawable name="stat_sys_upload_done">@drawable/stat_sys_upload_anim0</drawable>
    <drawable name="dialog_frame">@drawable/panel_background</drawable>
    <drawable name="alert_dark_frame">@drawable/popup_full_dark</drawable>
    <drawable name="alert_light_frame">@drawable/popup_full_bright</drawable>
    <drawable name="menu_frame">@drawable/menu_background</drawable>
    <drawable name="menu_full_frame">@drawable/menu_background_fill_parent_width</drawable>
    <drawable name="editbox_dropdown_dark_frame">@drawable/editbox_dropdown_background_dark</drawable>
    <drawable name="editbox_dropdown_light_frame">@drawable/editbox_dropdown_background</drawable>

    <drawable name="dialog_holo_dark_frame">@drawable/dialog_full_holo_dark</drawable>
    <drawable name="dialog_holo_light_frame">@drawable/dialog_full_holo_light</drawable>

    <drawable name="input_method_fullscreen_background">#fff9f9f9</drawable>
    <drawable name="input_method_fullscreen_background_holo">@drawable/screen_background_holo_dark</drawable>
    <color name="input_method_navigation_guard">#ff000000</color>

    <!-- For date picker widget -->
    <drawable name="selected_day_background">#ff0092f4</drawable>

    <!-- For settings framework -->
    <color name="lighter_gray">#ddd</color>
    <color name="darker_gray">#aaa</color>

    <!-- For security permissions -->
    <color name="perms_dangerous_grp_color">#33b5e5</color>
    <color name="perms_dangerous_perm_color">#33b5e5</color>
    <color name="shadow">#cc222222</color>
    <color name="perms_costs_money">#ffffbb33</color>

    <!-- For search-related UIs -->
    <color name="search_url_text_normal">#7fa87f</color>
    <color name="search_url_text_selected">@android:color/black</color>
    <color name="search_url_text_pressed">@android:color/black</color>
    <color name="search_widget_corpus_item_background">@android:color/lighter_gray</color>

    <!-- SlidingTab -->
    <color name="sliding_tab_text_color_active">@android:color/black</color>
    <color name="sliding_tab_text_color_shadow">@android:color/black</color>

    <!-- keyguard tab -->
    <color name="keyguard_text_color_normal">#ffffff</color>
    <color name="keyguard_text_color_unlock">#a7d84c</color>
    <color name="keyguard_text_color_soundoff">#ffffff</color>
    <color name="keyguard_text_color_soundon">#e69310</color>
    <color name="keyguard_text_color_decline">#fe0a5a</color>

    <!-- keyguard clock -->
    <color name="lockscreen_clock_background">#ffffffff</color>
    <color name="lockscreen_clock_foreground">#ffffffff</color>
    <color name="lockscreen_clock_am_pm">#ffffffff</color>
    <color name="lockscreen_owner_info">#ff9a9a9a</color>

    <!-- keyguard overscroll widget pager -->
    <color name="kg_multi_user_text_active">#ffffffff</color>
    <color name="kg_multi_user_text_inactive">#ff808080</color>
    <color name="kg_widget_pager_gradient">#ffffffff</color>

    <!-- FaceLock -->
    <color name="facelock_spotlight_mask">#CC000000</color>

    <!-- For holo theme -->
      <drawable name="screen_background_holo_light">#fff3f3f3</drawable>
      <drawable name="screen_background_holo_dark">#ff000000</drawable>
    <color name="background_holo_dark">#ff000000</color>
    <color name="background_holo_light">#fff3f3f3</color>
    <color name="bright_foreground_holo_dark">@android:color/background_holo_light</color>
    <color name="bright_foreground_holo_light">@android:color/background_holo_dark</color>
    <color name="bright_foreground_disabled_holo_dark">#ff4c4c4c</color>
    <color name="bright_foreground_disabled_holo_light">#ffb2b2b2</color>
    <color name="bright_foreground_inverse_holo_dark">@android:color/bright_foreground_holo_light</color>
    <color name="bright_foreground_inverse_holo_light">@android:color/bright_foreground_holo_dark</color>
    <color name="dim_foreground_holo_dark">#bebebe</color>
    <color name="dim_foreground_disabled_holo_dark">#80bebebe</color>
    <color name="dim_foreground_inverse_holo_dark">#323232</color>
    <color name="dim_foreground_inverse_disabled_holo_dark">#80323232</color>
    <color name="hint_foreground_holo_dark">#808080</color>
    <color name="dim_foreground_holo_light">#323232</color>
    <color name="dim_foreground_disabled_holo_light">#80323232</color>
    <color name="dim_foreground_inverse_holo_light">#bebebe</color>
    <color name="dim_foreground_inverse_disabled_holo_light">#80bebebe</color>
    <color name="hint_foreground_holo_light">#808080</color>
    <color name="highlighted_text_holo_dark">#6633b5e5</color>
    <color name="highlighted_text_holo_light">#6633b5e5</color>
    <color name="link_text_holo_dark">#5c5cff</color>
    <color name="link_text_holo_light">#0000ee</color>

    <!-- Group buttons -->
    <eat-comment />
    <color name="group_button_dialog_pressed_holo_dark">#46c5c1ff</color>
    <color name="group_button_dialog_focused_holo_dark">#2699cc00</color>

    <color name="group_button_dialog_pressed_holo_light">#ffffffff</color>
    <color name="group_button_dialog_focused_holo_light">#4699cc00</color>

    <!-- Highlight colors for the legacy themes -->
    <eat-comment />
    <color name="legacy_pressed_highlight">#fffeaa0c</color>
    <color name="legacy_selected_highlight">#fff17a0a</color>
    <color name="legacy_long_pressed_highlight">#ffffffff</color>

    <!-- General purpose colors for Holo-themed elements -->
    <eat-comment />

    <!-- A light Holo shade of blue -->
    <color name="holo_blue_light">#ff33b5e5</color>
    <!-- A light Holo shade of gray -->
    <color name="holo_gray_light">#33999999</color>
    <!-- A light Holo shade of green -->
    <color name="holo_green_light">#ff99cc00</color>
    <!-- A light Holo shade of red -->
    <color name="holo_red_light">#ffff4444</color>
    <!-- A dark Holo shade of blue -->
    <color name="holo_blue_dark">#ff0099cc</color>
    <!-- A dark Holo shade of green -->
    <color name="holo_green_dark">#ff669900</color>
    <!-- A dark Holo shade of red -->
    <color name="holo_red_dark">#ffcc0000</color>
    <!-- A Holo shade of purple -->
    <color name="holo_purple">#ffaa66cc</color>
    <!-- A light Holo shade of orange -->
    <color name="holo_orange_light">#ffffbb33</color>
    <!-- A dark Holo shade of orange -->
    <color name="holo_orange_dark">#ffff8800</color>
    <!-- A really bright Holo shade of blue -->
    <color name="holo_blue_bright">#ff00ddff</color>
    <!-- A really bright Holo shade of gray -->
    <color name="holo_gray_bright">#33CCCCCC</color>

    <drawable name="notification_template_icon_bg">#3333B5E5</drawable>
    <drawable name="notification_template_icon_low_bg">#0cffffff</drawable>

    <!-- Keyguard colors -->
    <color name="keyguard_avatar_frame_color">#ffffffff</color>
    <color name="keyguard_avatar_frame_shadow_color">#80000000</color>
    <color name="keyguard_avatar_nick_color">#ffffffff</color>
    <color name="keyguard_avatar_frame_pressed_color">#ff35b5e5</color>

    <color name="accessibility_focus_highlight">#80ffff00</color>
</resources>

perhaps this is what you're looking for: https://github.com/android/platform_frameworks_base/blob/master/core/res/res/values/colors.xml