Bed bugs are known to have color vision. The best evidence is a study by a group of scientists* who studied orientation to shapes and colors Bed bugs orient to black or red objects in preference to white or other colored objects. Bed bugs prefer vertical objects to horizontal ones.
The test arenas, bed bugs do not distinguish black and red. This has been confirmed by a study of the bed bug genome. The bed bug genome contains two opsin genes, one sensitive to ultraviolet and one sensitive to broadband long wave light. Bed bug visual reception does not extend into the red region making red and black identical. The bed bug visual system is similar to other True bugs (Heteroptera) and many crepuscular insects. Detecting shapes, may be more important to a creature of the night than detecting color.
*Singh N, Wang C, Cooper R. 2015. Role of Vision and Mechanoreception in Bed Bug, Cimex lectularius L. Behavior. PLoS ONE 10(3): e0118855.