I live in the Colorado Springs area. I am looking for a ground cover for an area that I have placed river rock. The area I have rocked is level at roughly 180 sqft. It would get at least 7 hours of direct sun. I am not looking to cover the entire area. The area looks very dull and plain. My idea (in phases) would be to break the monotony. Maybe incorporate a few large rocks (mini boulders). There is a lavender shrub in the middle of the length of the area. The area is between a patio and privacy fence. Eventually, I would like to add elements of color.

What would be my best choice (not limited to ground over):

Clay soil
Rock area
Direct sun
Minimal watering (once established - no irrigation in that area)
Moderate maintenance

In advance, thank you for your help.