OP mentioned West of Loveland/Fort Collins. Which would imply Geographic proximity to that area.

Cheyenne Mountain is well to the South near Colorado Springs.

Doesn’t mean it isn’t one of those Military/Government facilities that don’t Officially exist though

There’s also a whole lot of Private Land and small neighborhoods/communities before it shifts into the Rockies State Park.

Maybe someone is doing construction work and it’s the glow of high powered work lights. It’d be a tad unusual for work to be done at night but not completely unheard of. Especially if it’s a tight schedule