Change heading color

[waldyrious]

The current heading color, #317eac, is a light blue which is quite similar to the link color, #2fa4e7, and especially to the link hover color, #157ab5. This makes it easy to confuse them:

I would suggest either using a slightly off-blue color (e.g. a greenish blue like SeaGreen/#2E8B57) to make the distinction clearer, of even going the extra mile and using a complementary color from the orange-ish side. In this case I'd suggest (in increasing order of saturation): Peru/#CD853F, Chocolate/#D2691E, or DarkOrange/#FF8C00.

I would propose a PR myself but I wasn't able to figure out which file to edit.