Color UK primary routes green

[1ec5]

The transportation layer indicates a network of gb-trunk on officially designated primary routes in the United Kingdom (the ones with the green signs). Conventionally, these motorways are depicted in green on road maps. We’d need to deconflict this with the green for toll roads, perhaps by changing British toll roads to some other color (based on the network).

This would be an AARW-specific customization, because the upstream project has decided to vary only the shields based on route networks, in keeping with American cartographic convention.