Don't you dare slander purple! Putt-putt is purple, and my previous car was a metallic grape.
The first time I ever thought a car color was strange was when Ford Probes came in metallic orange. It really just depends on the type of vehicle, IMO. Some colors, odd they may be, look good on a particular car. Others look way out of place.
Although, I'm sure there have been "ugly" colors since the days of wayback. GM used to have that horrible lime green color that was most prominent on Impalas and Caprices. My aunt had an Impala of that color.
GM currently offers a color called Cappuccino. It seems to be most prominent on Monte Carlos. It's actually a nice color.