change the color scheme from the config file

The current color scheme is white/gray with a highlight color (purple).
https://github.com/codeforboston/finda/blob/gh-pages/styles/style.css <- every note about brand primary/accent color.

It would be cool to just have a "purple" property in the config file, and then build the needed css properties in js. This would involve being able to darken certain specified colors on the client side too.