CSS colours of the bands, the innermost band first, starting over after the last. An empty list
counts as unset: the bands then ramp from the map's accent toward its land colour, the other way
round for 'inverted', which deepens away from the origin.
Remarks
Bands are ranked per origin, so with several origins the ranges of the same rank share a colour.
The fill of the ReachableRangesModule bands.