For Zone 5b in Denver, a pool actually fits really nicely if you pair it with cold-hardy, low-water plants. The layout works well with a curved edge and some structure around it things like spirea, boxwood, Russian sage, catmint, and hardy hydrangeas do great there and keep the space colorful without much upkeep.
I mocked up a quick idea just to show how a pool + simple planting around it could look in your yard: https://app.neighborbrite.com/s/YSGQpzaoMQk
