Its done through String (Text) embedding.
Syntax |cffxxxxxx(Insert some text here)|r
The xxxxxx is the Hexadecimal representation of the color you want (RGB format).
Example |cffffcc00Soviet Power Supreme|r
Should output
Soviet Power Supreme
Hex is 0-9, A-F. Use a paint program to find the color you want and use Calculator to recover the Hex digits.
There is also a program that generates this for you called wc3color.