Paint mines is a county managed open space as well as a Geological park. The clay formations are mixed with oxidized iron which creates the rainbow colored statues.
The open space also makes for a great geological site as it has been used for the last 9,000 years. It served as a place for indians to make colored paint. The canyon walls also made for a place to funnel buffalo into for hunting.
Painted mines has 3 parking lots. The upper and lower parking lots are connected by a mile long trail that goes through the clay formations. The middle parking, inbetween the two, has a small walk to an over look.
There are a couple trails that go all over the park, but the main trail is Paint Mines Interpretive trail loop. There are colorful clay deposits all over the open space, but the biggest and best deposit is on the south west side just below the overlook. It is a very easy well maintained trail. The main deposit can be easily accessed from either parking lot. I would not say one parking lot is better than the other.
If planning on going during the winter, just remember that some of the colorful deposits may be covered in snow.