It has always been possible to color TeX output. To do so, add the line

  `\usepackage{color}`

to the preamble, and insert a line like

  `\color{blue}`

before typesetting begins. To color a limited section of text, use a command like

  `{\color{red} This is very important!}`

To define custom colors, use a command like

  `\definecolor{mycolor}{rgb}{0.2, 0.7, 0.8}`

Users may be familiar with a list of defined colors with names like "BrickRed"; these named colors were defined automatically for the dvips driver. To use them generally, use the syntax

  `\usepackage[dvipsnames,usenames]{color}`

When output is colored, the output may be difficult to read on the preview screen. TeXShop has hidden preferences to set the background color of the preview window. This background color will not appear when the document is printed. To set the background to gray, issue the following commands in Terminal:

  `defaults write TeXShop Pdfbackground_R 0.5`
  `defaults write TeXShop Pdfbackground_G 0.5`
  `defaults write TeXShop Pdfbackground_B 0.5`

Change 0.5 to 1 to get back to white. If you find yourself changing the background often, create an Applescript macro named "PDF background gray" with the Macro Editor using the following text:

  `--AppleScript`
  `do shell script "defaults write TeXShop Pdfbackground_R 0.5"`
  `do shell script "defaults write TeXShop Pdfbackground_G 0.5"`
  `do shell script "defaults write TeXShop Pdfbackground_B 0.5"`

and create a similar macro named "PDF background white".

Advanced Help
Colored Text in TeX