I actually wondered that for a long time and got an answer a couple years ago. Missed a cat by a couple feet 2 seasons ago. I had one trap at a toilet (lesson learned to gang set toilets) and the cat dropped a turd near my trap the night before I checked (had him on cam). The next two weeks was very cloudy and it rain lightly a couple times and the turds were that light blue, and almost white (what I use to to think was a month or two). By the next week (not as cloudy) it was white, and a couple weeks later when I pulled the trap the turds we chalky. Helped me realize how quick they turn and I can only imagine how quick they turn when it’s blazing hot, dry, and sunny. This wash has been washed out about a month before I found it. Now some of the turds could have been washed down from farther up, but the few turds near the tree would have been high enough to not get washed out so I know they visit this spot. Plus I don’t think they only poop at toilets. I’m sure some (just my opinion and have no proof) just pee. Haha or maybe that’s just what I tell myself to make me feel better haha.

I'm following this thread and will copy anything that works.

If I may. I have always been told that white was a good thing.