Adapting Nav Text from Transparent Background to White Background

Dear Team Kriesi:
Love the theme. Keep up the great work.
Question: I’m sure there must be an easy way to do this, but I haven’t figured out which CSS to tap in order to do it. Basically, I have a transparent header on my home page (which is dark), so I need the nav text to be white. But, once I scroll, I have the header change to solid white, so then I need the nav text to be a dark color. How can I easily distinguish between the nav link color and hover for the transparent vs. the nav link color and hover for the white page?
Please advise.
Thank you.
Tim