Well, you can do /colortest in your server to get a list of colored numbers, and each one of these refers to an escape code like so:
\c0 = red
\c6 = white
and those just go in the message text.
But if you were using centerPrint, in the message string you can do: <color:FF0000> to do red, FFFF00 to do yellow, and all the other infinite combinations.