You have a good chance of catching the last of the aspen color. The dates you mentioned are generally considered past "peak" color. But if the weather holds, the leaves often hold on into October.
There are some nice views including aspens and Longs Peak just up the trail leading North from Bear Lake. Sprague, Bear and Dream Lakes are all very scenic. Also, the tundra up on Trail Ridge Road should provide some nice fall colors. Try the Forest Canyon, Rock Cut and Gore Range Overlooks.
The
RMNP Forums? is a great resource with nice people. And be sure to check out Erik Stensland's
Images of RMNP. He specializes in RMNP, has a gallery in Estes Park, and has some really beautiful images (he's also a good friend of mine).
Hope this helps.