If you live southwest Litteton. The Ridge and Peak and Lilly Gulch recreation centers offer Indoor lap, Competion Diving, Warm Therapy, as well as childrens indoor area. There link is at http://www.ifoothills.org/aquatics.asp Once you join you also have access to 4 outdoor pools. Now the outdoor pools are not lap style pools. They are more for family recreation.
Wheatridge offers indoor and outdoor as well they can reached at http://www.ci.wheatridge.co.us/index.aspx?nid=606
City of Golden has a great center as well they can be reached at
Northglenn, Parker, Lakewood and others cities have facilties as well.
In the Centennial area Lifetime Fitness on Dry Creek Rd. in the western area of Centennial (where I belong) has a great outdoor and indoor pool for members. If you are in the eastern area of Centennial near Parker Road then the Lifetime Fitness in the City of Parker has a similar facility. Outdoor pools in Colorado are typically only open from Memorial Day to Labor Day. Almost every neighborhood in any part of Centennial has access to an outdoor pool during these months and these neighborhood pools have designated lap lanes and "adult swim" periods every hour.
My grandson is a year round club swimmer and indoor pools are few and far between relative to the number of swimmers which makes joining a fitness club like Lifetime or 24 Hour your best for year round swimming. I don't think any nearby 24 Hour facilities have an outdoor pool.