Yeah, they need places to hide to be happy... But they will change colors pretty often depending on mood and their interactions with other fish/loaches. The biggest (head honcho of the shoal) loach in your tank will normally stay somewhat discolored. You can also feed them cooked mussels, I can't imagine some of it wouldn't fall down there for them. They are norm like $2 a bag, pre-cooked in the frozen section of the seafood... just rinse/defrost under warm water and just pull out the mussel from the shell and toss it in there. Raw/Peeled shrimp is also useful, but a tad more expensive than mussels.
Also consider this food, since its small and sinks and should not cloud water if you slightly overfeed to get food down there to them:
http://www.amazon.com/Life-Spectrum...-1&keywords=New+Life+Spectrum+Thera-A+Formula
Oh and the min # of loaches in tank should be no less than 5, at the bare min. They very much need other loaches around to be happy....
