I like the bright red.
It is historically correct for 1916 and earlier.
Yes there was a directive to stop painting the caboose cars bright red, but that does not mean that all the cabooses were repainted right away, I am sure that it took a few years before they got around to repainting them. Also as others pointed out there is evidence that the directive was not always followed, and at least one caboose was painted in bright red in 1918.
Therefore I believe we are open to some interpretation or even creative licence on this.
If we could find records as to the dates after May 24, 1916 each caboose was repainted, or even if the new directive was followed when the caboose was repainted, I think we could then get a historically accurate color for a particular caboose on a particular day or year.
Black and white photos may even help as the bright red would probably be easier to pick out from a B/W photo than other colors that are often energetically debated on this board.
I also like this thread and find it entertaining reading.