The last windy.com update has cleared most of the mappings between altitude and colour.
Maybe this was done for users who are sailing boats and don't need altitude data, but aviation users do need that data, in lots of steps. It used to be like that but somebody went in there and cleared the tables for cloudbase and cloud tops.
For cloudbase, one needs steps of about 200ft from 0 to 2000ft, then in say 500ft steps to 5000ft, then 1000ft steps up to 35000ft.
For cloud tops, one needs steps of about 500ft up to 5000ft and then 1000ft steps up to 35000ft.
It used to be something like that.
As the EuroGA.org thread shows, some expert users have produced their own mapping tables, but this is complicated.