People are talking about going to the mountains for fall colors. I don't understand that. Back East, most of the mountains were covered by deciduous forest which blaze into color during the fall but even there, at the higher altitudes in the Blue Ridge, they turn into alpine forests of assorted evergreens.
Here, the Rockies gain altitude quickly from east to west and become evergreens and aspen. The aspen provides patches of bright yellow and there are some colorful low shrubs, but most of the color are in the towns where many of the trees are from other parts of the world.
The photos above are from Centennial, where the residential areas have colored up nicely. The plains host some nice fall colors where there are trees. Willows, cottonwoods, and sumacs grow along streams and produce bright yellows and reds.
The color pigments in tree leaves are associated with sugars that have been stored up in the plants. They're always there but chlorophyll, the pigment that converts sunlight, carbon dioxide and water into stored energy in the form of sugars, is more important to the tree so the green drowns out the other colors. When the Earth tilts away from the sun and trees get ready for less light and colder temperatures, the deciduous trees stop producing as much green chlorophyll before dropping the leaves altogether. Assuming that a landowner doesn't rake up the leaves for a landfill, they rot and add nutrients to the soil for future use.
Last year, I wanted to photograph the Highline Canal Trail in each season. Unfortunately, we didn't have a fall as far as the trees were concerned. To produce sugars and pigments, trees need rain and last year was a rather dry year. It suddenly became cold, the trees went brown, and the leaves came down in a matter of days.
This year, we're getting colors, so, if you want fall colors, check out the aspens, but also visit the overlooks and view the towns like Kitteridge, Vale, Golden, and Boulder, and don't miss the cities of the plains.
How are the fall colors in your area? Do they seem to be related to the weather, and how? There are many ways to study leaf colors and, for that, I will recommend that you visit the Science Buddies website (https://www.sciencebuddies.org) and search for projects concerning leaf colors.