Hi Toby,
Glad you want to see Colorado!
This year has been oddball weather, all year... usually we're very dry, and this year we have had record quantities of rain, the place looks and feels like the east coast. I wouldn't begin to try to predict what will happen with the foliage this year.
The reservoirs have been flooded. That means the trees around Chatfield Reservoir (for example) have spent the spring & summer 3 to 4 feet deep in standing water. The trees look pretty alive to me right now, but I'm told that will eventually kill the trees, so who knows what that means RE: timing of fall colors.
For lack of a better plan, I would suggest you come earlier in the season, rather than later, if you want to be sure you have not missed the leaves. Once you get here, figure out where (which altitude) the colors are that weekend and go there. Call the various state parks, the rangers will be able to tell you if their park has good foliage or not. If you're staying on the front range, I'm pretty certain you'll find someplace that has golden aspens at their peak within an hour or so drive. If you wait till the end of October, the leaves could - possibly - all be gone.