If you manage to find us enough players to make the top 50 purple I'll give you more ranks. For now I think, adding more colors or switching up the system will be simply more confusing.
You can still make design suggestions of course. We'd probably have to switch to a system like Istrolid, where rank icons only depict rating from a certain point onwards. This would allow using shapes to differentiate the top players.
PS: Looking at the trend, the amount of purples is starting to shrink again.
