We visited Maroon Bells at the end of September and hit the jackpot in terms of autumnal colours. The weather was perfect- chilly early in the morning, but the sun warmed us later. The sky was brilliant blue and a wonderful backdrop for the simply stunning Maroon Bells. Our jaws just dropped at the beauty of this place. We had such an array of colour: gold, yellow and red, mixed in with some green, the snowcapped Bells themselves and the blue sky. All this incredible beauty was reflected in the lake. I felt like I was on a movie set, it was so unreal!
My tip would be to get there early, that way you can drive your own car into the park. After 9am, the gates are shut to incoming private vehicles and you have to take a bus from Aspen. It also gets pretty busy with everyone trying to get that perfect shot of the Bells, so it's better to be there earlier rather than later.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.