I apologise in advance for the graphic nature of this question. I guess it just had to be asked.
I am looking for a way to make the feces of my alien vertebrates some color other than brown or green. In our Terran vertabrates, bile that is broken down in the gut along with items in the diet affect the color of fecal matter. We usually see green, rust, or the 'classic' brown unless something unusual such as a beet was eaten. My first thought when finding an answer to this question was to find an alternative to bile for breaking down fats into fatty acids. I am looking for something that would change the color almost regardless of what was eaten, as bile does. Anything that would change the color in carnivores, herbivores and everything in between would work. As long as the feces will be distinguishable from Terran feces, it should work.
Thanks for bearing with this one.