Syntastic is a great linter plugin for Vim, catching syntax errors while you write code in nearly any language (even Latex). Since I spend most of my days editing in Vim, the obtrusive gray bar became intolerable. Here’s another user’s screenshot from the github issue:

Adjusting the color was more involved that I imagined…

It’s not Syntastic; it’s the colorscheme

This was the key insight. All you need is to tweak a single line in the solarized colorscheme (solarized.vim file): see here

et voila!