My apologies for not responding sooner, this issue has been on my list to chase up for a while. The reason for the difference being observed on the rocky worlds is the change to the new material system - in theory this is more accurate as it uses the chemical properties to determine the colour (obviously I'm simplifying a bit here!), however the problem is that those colours were based on Earth standard colouration for those materials, and most of those are beige/brown rather than the colours you might observe in the myriad of other possible conditions. We're currently working on a more flexible material system, and this will necessitate a fresh balance pass on these. That's not going to be in 2.3 though.