Never saw the Katy in its heyday, but found a few cars over the years. Here's a tank car in red at Council Bluffs, IA 15 or so years ago: A boxcar in the UP heritage collection in Cheyenne, about 15 years ago: A Katy hopper about to cross under the C&S overpass in Cheyenne at MP 511. Ignore the UP shield, the shadows are all Katy!
Just west of the Monte Vista depot next to the yard limit sign (Google coordinate 37.583332, -106.151245), maybe still owned by Donald Shank of D&RG which has been up for sale since 2015. Boxcar Red Collection