While I am still waiting for approval to Google Adsense I was wondering if there is an option to customize the color, text size, and font of the adsense ad when we log into adsense management?
You cannot change so many things in adsense code. You can make your own color, and background color. That is all what you are able to.
I bet you "could" change attributes by specifically hitting certain CSS attributes of their ads but I guarantee it is against their TOS. You could see what can be changed by applying the css * { css attributes here }. Now that I think about it - they have JS write an iFrame now so it would take some massive hackery - better luck next time
Changing font is possible if you would hack the code. But it is against TOS to change anything. If you were a premium publisher you could do lots of things, such as custom fonts, font sizes, ad unit sizes... but you have to be BIG (years of work) to become a premium publisher.