megnicholas on "[Plugin: Contact Form Clean and Simple] Change font color on contact form"

I assume you mean the placeholder text?

To change that to white you need to add this to the bottom of your theme's stylesheet.:

::-webkit-input-placeholder { color:#fff!important; }
::-moz-placeholder { color:#fff;!important } /* firefox 19+ */
:-ms-input-placeholder { color:#fff;!important } /* ie */
input:-moz-placeholder { color:#fff;!important }

http://davidwalsh.name/html5-placeholder-css

If you don't know which file to add this to, please ask your theme developer for support as they really should have been able to help you with this in the first place!