[Ed]

I did a google image search for "red moss", "orange moss" and "yellow moss" and there are some nifty mosses which seem to occur in those respective colors naturally. Unfortunately, most pics on google don't have the binomial name represented.

Has anyone had any experience with any other-than-green moss varieties? (besides the common "british soldier moss" or "haircap moss")

British soldier moss (Cladonia cristatella) isn't a moss but a lichen. On the same google image search many of the examples were of lichens, or sphagnums that are growing in direct sun, but there was one true red moss Bryium minatum but the conditions in which it is growing do not look like they would transfer to dendrobatid style enclosures. You can consider trying some of the red or yellow selaginellas.

Ed