Reddish Green
The following figure is from “REDDISH GREEN: A CHALLENGE FOR MODAL CLAIMS ABOUT PHENOMENAL STRUCTURE” by Martine Nida-Rumelin & Juan Suarez (link to pdf) and reproduces stimuli utilized in experiments in which paradoxical visual experiences were induced, such as experiences of a single color patch being colored reddish green.
Some subjects report “seeing a homogeneous color phenomenally composed of red and green whose components are as clear and as compelling as the red and blue components of a purple.”
The phenomenon is induced by presenting equilluminant colored stripes in images stabilized via use of an eye-tracker. The experiments reported are from Billock et al. which reproduce experiments from Crane and Piantanida.
See:
Billock, V. A., Gleason, G. A., & Tsou, B. H. (2001). “Perception of forbidden colors in retinally stabilized equiluminant images: an indication of softwired cortical color opponency?” J Opt Soc Am A Opt Image Sci Vis, 18(10), 2398-403.
Crane, H. D., & Piantanida, T. P. (1983). “On Seeing Reddish Green and Yellowish Blue.” Science, 221(4615), 1078-1080.
See also my “Hyperbolic Mary“