Highlight your text by selecting it and click on the icon that shows an "A" with a bar under it. It's to the right of the U(underline) icon. From there, select your text color. If you want to remove the effects, highlight the text and then click on the icon that shows a "T" with a small x in it.
Alternatively, you can add the code manually:
It says "Help" at the bottom of the page. You can click on that and then click on BB Codes to learn about how to change colors manually. This'll get you here: http://mcpz.net/index.php?help/bb-codes