In order to change the font color for the content in MediaWiki, you should edit the skin's main.css file.

For example, if you are using the default Monobook skin, the file you should edit is:

/home/user/public_html/skins/monobook/main.css

Look for the following code:

#content {
    background: white;
    color: black;   
    border: 1px solid #aaa;
    border-right: none;
    line-height: 1.5em;

You should edit the color:black; line. For example, if you wish to change the font color to blue, the line should be changed to:

    color: blue;  

You can also use hex codes for the colors of your MediaWiki content.