Catch the sunset where the Arkansas River enters the Pueblo Reservoir at Lake Pueblo State Park.
The sunset is great all around the park, but if you're looking for a bit of an adventure and one of my favorite unknown spots follow along below:
Entering the North entrance of the park turn right onto the gravel road right before entering the park gates. Continue down the gravel road through the prairie leading up to the water. Enjoy the sun coming down over the San Isabel Mountain Range in the background. When the road splits turn left, then at the second split make a right (You can explore all these gravel roads leading to different coves along the Lake, My route is just a suggestion!).
Put it in park, turn on some music and enjoy the sunset from your car or some lawn chairs.
For photographers set up your gear and enjoy the colors as the sun sets over the mountains and lake.