Most cabooses are a form of red or boxcar red, bobbers no exception. There are some color schemes from that era on standard cabooses, so was the same true for bobbers? UP had its yellow red on bobbers too. Google yields only black and white photos. And loads of models. What colors did exist on bobbers?
What colors did exist on Bobbers? Pretty much all the colors on all other types of cabooses. What ever the railroad had on hand that was cheapest, easiest to do, and follows some sort of protocol if need be.
I have a bobber caboose that I got in a box of used trains. It’s just cheap sheet metal, painted red. I’ve never run it. It has one horn hook. The caboose has no markings.
Cabooses are painted whatever the standard is for the railroad, 4 wheel or 8 wheel. If the railroad had bobber cabooses they would be painted standard railroad colors for the time.
Keep in mind some states outlawed bobber cabooses pretty far back. Here in Minnesota, the Railroad Act of 1911 (IIRC) required cabooses to be at least 24’ long and have at least two four-wheel trucks. So I suspect relatively few bobbers were around long enough to get colorful post-war type decoration.
BTW the Missabe Road’s classic wood cabooses, as modelled in HO by Walthers, were the result of the railroad taking two bobbers and combining them into one caboose so they met the legal requirements. You can see how it was originally a bobber with the cupola between the two windows, and then they added the non-cupola part of another one with one window to get it to length.