If you are using the RTE (Rich Text Editor), then you can highlight the words and select a color from a drop down box. It works a lot like any "word" program. There is a box above the text editor that lets you choose things like font and font size. In that block, the button that looks like an "A" allows you to choose font color.
If you are not using the RTE, then I believe you have to add code manually. This would look something like putting "<color>" before and after the words you want to change color. Note that it would not change the color until you posted or play tested in this case. Each color has a coding version you need to know. For example, I think "black" is "blk".
I am one of the strange people that uses the RTE, so someone else can probably help you more if you don't.
