Great job! I'm also in favor of slight adjustments to make the color scheme a bit less aggressive. But overall: super neat!
While I do like the explanation text under "What is Gridcoin?" ... may I suggest to insert a "easy-as-one-two-three" kind of summary before that?
Something along the lines of:

1. Simply install the Gridcoin wallet and use a trusted exchange to become an investor.
2. As a Gridcoin miner, you get crypto currency for supporting ongoing distributed computing projects.
3. With Gridoin, the electricity that is needed to run the network does something good in addition to providing a crypto-currency.
   Let's earn money for supporting science.

This way we could have a really simple summary before visitors get confronted with the slightly technical "What is Gridcoin" text body as it is now.