Black fixtures. etc.
You'll think I'm off the wall on this one, but......
My father, who was a physician and who had colon cancer once and fortunately caught it early enough to survive it, advised us to only use white toilet paper for the same reason I will suggest you consider both white paper and white toilets - You will get a heads up if you have blood in your stool or urine. (Incidentally, black tarry stool, as I understand it, is also a sign of bleeding, but from a different location in the intestines.)
Could save, or prolong your life. Could just be hemmorroids, but could be Cancer, bladder/prostate problem, etc. Wouldn't you want to know?