Change Toolbar color in Appcompat 21

again this is all in the link you supplied

to change the text to white all you have to do is change the theme.

use this theme

<android.support.v7.widget.Toolbar xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
android:id="@+id/activity_my_toolbar"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:minHeight="?attr/actionBarSize"
android:background="?attr/colorPrimary"
app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar"
    app:popupTheme="@style/ThemeOverlay.AppCompat.Light"/>

UPDATE 12/11/2019: Material Components Library

With the Material Components and Androidx libraries you can use:

• the android:background attribute in the layout:

  <com.google.android.material.appbar.MaterialToolbar
      android:id="@+id/toolbar"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"
      android:background="?attr/colorPrimary"
  

• apply the default style: style="@style/Widget.MaterialComponents.Toolbar.Primary" or customize the style inheriting from it:

  <com.google.android.material.appbar.MaterialToolbar
      android:id="@+id/toolbar"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"
      style="@style/Widget.MaterialComponents.Toolbar.Primary"
  

• override the default color using the android:theme attribute:

  <com.google.android.material.appbar.MaterialToolbar
      android:id="@+id/toolbar"
      android:layout_width="match_parent"
      android:layout_height="?attr/actionBarSize"
      android:theme="@style/MyThemeOverlay_Toolbar"
  

with:

  <style name="MyThemeOverlay_Toolbar" parent="ThemeOverlay.MaterialComponents.Toolbar.Primary">
    <item name="android:textColorPrimary">....</item>
    <item name="colorPrimary">@color/.....
    <item name="colorOnPrimary">@color/....</item>
  </style>

OLD: Support libraries:
You can use a app:theme="@style/ThemeOverlay.AppCompat.Dark.ActionBar" theme as suggested in other answers, but you can also use a solution like this:

<android.support.v7.widget.Toolbar
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    style="@style/HeaderBar"
    app:theme="@style/ActionBarThemeOverlay"
    app:popupTheme="@style/ActionBarPopupThemeOverlay"/>

And you can have the full control of your ui elements with these styles:

<style name="ActionBarThemeOverlay" parent="">
    <item name="android:textColorPrimary">#fff</item>
    <item name="colorControlNormal">#fff</item>
    <item name="colorControlHighlight">#3fff</item>
</style>

<style name="HeaderBar">
    <item name="android:background">?colorPrimary</item>
</style>

<style name="ActionBarPopupThemeOverlay" parent="ThemeOverlay.AppCompat.Light" >
    <item name="android:background">@android:color/white</item>
    <item name="android:textColor">#000</item>
</style>

Hey if you want to apply Material theme for only android 5.0 then you can add this theme in it

<style name="AppHomeTheme" parent="@android:style/Theme.Material.Light">

        <!-- customize the color palette -->
        <item name="android:colorPrimary">@color/blue_dark_bg</item>
        <item name="android:colorPrimaryDark">@color/blue_status_bar</item>
        <item name="android:colorAccent">@color/blue_color_accent</item>
        <item name="android:textColor">@android:color/white</item>
        <item name="android:textColorPrimary">@android:color/white</item>
        <item name="android:actionMenuTextColor">@android:color/black</item>
    </style> 

Here below line is responsibly for text color of Actionbar of Material design.

<item name="android:textColorPrimary">@android:color/white</item>