From Wikipedia:

"The Painted Hills is a geologic site in central Oregon that is one of the three units of the John Day Fossil Beds National Monument. It totals 3,132 acres (12.67 km2) and is located 9 miles (14 km) northwest of Mitchell, Oregon... The layers of color for which the site is named can be traced back to cycling periods of wet and dry climate conditions associated with the transition from the Eocene epoch to the cooler, more temperate Oligocene epoch. The different layers of colors are due to the soil being composed of a combination of mudstone, siltstone, shale and lignite."

A short video (03:11 in duration) of this unique area has been posted on my YouTube channel. Here's the link:

https://www.youtube.com/watch?v=v2wyi-gNq3s