Went on another dog walk with my brother and his pug yesterday evening. The tan S2+ (519A 5700K) I was carrying on about 10% power was fantastic for lighting up the unpaved road ahead of us and avoid any patches of soft mud from the rain of the previous night. Actual water puddles are obvious even in the dark, but with the rust-red dirt that we have around here, damp mud is not as obvious.
I also tried my 3500K S21A (also 519A) that I'd forgotten in the pant pocket before going out, but it didn't do as good a job. The color of the soil meant there was next to no contrast against the dirt and mud. It's a great light for buildings, foliage and so on, but not for this specific use case. The 4000K of an FC40 is the warmest I can go for walking dirt paths.