Mapper frontend legend does not match colours of features

[spwoodcock]

• We are using available css vars for the feature colours.
• The buildings should definitely be green instead of blue I think.
• We should ensure the colours match.
• In the future, we will provide task area colours with a globally loaded css var in hotosm/ui, e.g. --hot-task-ready.
• However, as the feature colours are unique to FieldTM, I think we should set our own vars, e.g. --hot-entity-ready: var(--another-defined-colour-here) and --hot-entity-in-progress: var(--another-defined-colour-here) (for OPENED_IN_ODK), etc