Angela -
coincidentally, I am a member of the board - haven't been on in a few weeks...but, was googling (I know, reliable) the same exact thing and your post came up!
For about 2-3 weeks now, I've had a yellow-orange coating on my tongue (no bad breath or anything). It comes off when I brush; however, sure enough the next night, it is back - regardless of what color food I've eaten throughout the day. It's odd to say the least.
I'm not on any medication at all... so, if we have the same issue going on, it couldn't be medicines. Let me know if you find anything out!
I've read that a yellow-orange coating on tongues could be a sign of acid reflux; however, that is mostly if it is evident in the morning. Our issue seems to be at night only - at least, mine is.
Best of luck!
Jade