Add color blind mode for bike map overlay

[nvkelso]

Feedback around the launch suggests we should tweak the colors &/or create a separate set of colors that is more friendly to those needing universal access.

[nvkelso]

The Washington, D.C. bike map has decent black and white legend (or we just modify the bike map's default colors):

http://www.godcgo.com/Portals/0/DC-BicycleMap_2016.pdf, http://www.waba.org/resources/maps-and-documents/