Go to:

\templates\crystal\css\html.css

find this part of the script: towards top.

    font-family: "Trebuchet MS", Tahoma, Arial, sans-serif;
    font-size: 13px;
    line-height: 22px;
    color: red; (change to your own color)
    position: relative;
    z-index: 0;

Change:
color: red;

To what ever color you want.