More Color Tweaking

Since I felt like I was neglecting the Pressbook Collector site, I decided to clean up the colors and fonts a bit. There weren't a ton of changes. I just tried to match the colors on the site with the colors in the header (as much as possible).

I also changed some of the fonts in the CSS file to make it look more like the inside of a pressbook. Hopefully it looks a little bit better. I'll start working on a bit of SEO next.