Option to adjust colour scheme based on colourblindness

A setting that can toggle between standard (no colourblindness) and the main types of colourblindness (red-green, blue-yellow, etc.). May need to confer with Access Collective for specific colourblindness options to consider.
This would affect the iOS colour scheme (back links, etc.) and the Google Map itself.

Start by locating the iOS colour-scheme setting and the Google Map integration, then review how back links and map colours are currently selected. Consult Access Collective about the colourblindness options to support, and consider the work done when both the iOS interface and Google Map use the selected scheme.

Written by the indexing model from the issue text.