There is already a stocking level issue with Rainbow versus Xeno
Having never seen the pyramids in an actual store since 2003 (when they were still monochrome), I don't know much about this personally, but it seems interesting. Especially since I imagine that if one color were more popular than the other, it would be difficult to complete a 5house set.
I know the crazy good martian special made the store purchase an equal number of xeno and rainbow treehouse sets, I wonder if stores ended up sitting on piles of xeno for instance.
As for making a separate product for xeno coasters, one counter point to that is that it would become a real pain to need to produce 2 versions of every pyramid product from here to eternity. There are already people thinking in terms of the sub-xeno IceTowers box set color scheme too.
People with more information on sales numbers and things like that would know better as to the xeno/rainbow sales ratio I'd imagine.
-Evan, who is interested by the strangest of workings in the game industry