Change Emacs syntax highlighting colors

Two ways - you can install the package color-theme, which has lots of nice schemes to select and is easier to do it by hand. The by-hand looks like this (in your .emacs file)

(custom-set-faces
   custom-set-faces was added by Custom.
   If you edit it by hand, you could mess it up, so be careful.
   Your init file should contain only one such instance.
   If there is more than one, they won't work right.
  '(default ((t (:inherit nil :stipple nil :background "lightyellow2" :foreground "gray20" :inverse-video nil :box nil :strike-through nil :overline nil :underline nil :slant normal :weight bold :width normal :family "liberation mono"))))
  '(background "blue")
  '(font-lock-builtin-face ((((class color) (background dark)) (:foreground "Turquoise"))))
  '(font-lock-comment-face ((t (:foreground "MediumAquamarine"))))
  '(font-lock-constant-face ((((class color) (background dark)) (:bold t :foreground "DarkOrchid"))))
  '(font-lock-doc-string-face ((t (:foreground "green2"))))
  '(font-lock-function-name-face ((t (:foreground "SkyBlue"))))
  '(font-lock-keyword-face ((t (:bold t :foreground "CornflowerBlue"))))
  '(font-lock-preprocessor-face ((t (:italic nil :foreground "CornFlowerBlue"))))
  '(font-lock-reference-face ((t (:foreground "DodgerBlue"))))
  '(font-lock-string-face ((t (:foreground "LimeGreen"))))

...

etc. etc.

You can also type

`M-x customize-face RET`

which will give you all the customizations to set, ultimately end up in your .emacs file.

I find it easiest to use color-theme for this sort of thing.

But if you don't want to do that, put the cursor over the offending text, and hit M-x customize-face. It should default to the face that the cursor is over.

See 49.1.6 Customizing Specific Items.