We're glad you've been enjoying the large amounts of recolours :) We tend to prefer releasing initially in limited colours because there have been so many occasions in which we've loved an item but then the userbase has not liked it! Seeing the excellent response to the added colours we've been doing, we're happy to consider adding extra colours to certain sets in the future - as long as there is support behind it.

(Check out the topic Reduce, Reuse, Recycle, Recolour if you want to add your support to an item - we can't guarantee that it'll get done of course, but it's the best chance for getting these sorts of requests noticed)