I guess that makes sense, but it would mean that his bowels were extremely hot. I can't imagine what his bowel movements would have been like. He doesn't appear to have a penis, so perhaps he had a cloaca like the birds on our own planet, where his urethra and anus were combined, and his bodily functions would be merged. If that is the case (and I think it is, based on my research) his feces would have high amounts of uric acid and nitrogen. This would lead to the white color we see when a bird leaves its droppings on our car's windshield. I think the heat factor could also affect Watto's anal or cloacal excretions, to say nothing of Tattooine's atmosphere, where inhalation of various gases could lead to a striking change in color. Lucas has decided not to add close-ups of Watto's bunghole, which has created to myriad problems in understanding Toydarian anatomy. And its worse than you think, because Star Wars is set long ago, so we don't even know what the atmosphere was like in the present time, much less the past. Star Wars loves to omit crucial details. We never saw Padme's shitmaker either, which has led fans to speculate that Amidala's throne was a toilet of sorts, and her large dress held a colostomy bag setup, with her white geisha make up actually being a clever ruse to hide her facial flushing whenever she has to pass a deuce while simultaneously being on video chat during negotiation with the Trade Federation or Senator Palpatine...
