Moab is miles upon miles of desert with a few trees clinging to life on the edge... definitely not "fall colors" material. But Dead Horse Point and Canyonlands are beautiful desert scenery. If you go up the Colorado River from Moab there are some trees along the "La Sal Mountain Loop", but I don't know if they'd show much color, as I don't recall what type of trees they were.
Another source for Teton/Tellowstone information might be wyofoto.com, but your best bet would probably be to speak to the rangers at the parks.