OsmColors

Maps OSM tags to a wall Color. Tries, in order:

1. building:colour or colour parsed as #RRGGBB/#RGB/CSS-name.

2. building:material mapped via a small lookup table.

3. A category tint inferred from historic / tourism / amenity / certain building=* values (so e.g. museums, churches, and town halls read differently from generic residential at-a-glance).

Returns null when nothing matches, leaving the caller free to use a default. The lookup tables stay small on purpose — they cover what's frequently tagged in OSM. Unknown values are treated as "no opinion" rather than guessed at.