Though we think of cabooses as being red in color, they have actually been painted almost every color under the sun. In the old days, many conductors who were assigned a waycar, could paint and decorate them any way they chose - within reason of course. Although the tradition on many railroads was that the caboose should be painted a bright red, on many lines it eventually became the practice to paint them in the same corporate colors as locomotives (see photos on our Caboose History page).
Norfolk & Western Railway's C31-class cabooses, of which Warrenton's #518554 is part of, originally came painted in a blue color with yellow markings. This blue, somewhat affectionately referred to as Pevler blue, was named after N&W's 10th president Herman Pevler. The cars were re-painted in the classic red which you now see on #518554 in the latter part of the 1960s.
If you get a chance to visit Lancaster County, Pennsylavania, be sure to visit the Red Caboose Motel. There, you will not only get the chance to sleep in a railroad caboose, but get to see 38 cabooses all painted in their original liveries!
(Photo of N&W 518675 by Kevin Sprayberry. Used with permission.)