Colour may turn out to be the new "WTF" -- Although, the specimens do look great. It is hard to see them as a thing that will take off with graphic designers though. Few of the designers I know have heard of coloured fonts or layered fonts for that matter. I'm not convinced that many of those who've prurchdaed licenses for any of the several layered fonts I have on the market, did so with the intention of using them as such.
Fonts will, I think, forever be positive and negative shapes. Colours are nice, but as decoration. Not a core feature... with a couple probable exceptions I can think of, such as brand specific inclusions.