虽然通常不会看到红色和绿色，也不能看到蓝色和黄色，但视觉科学家Hewitt Crane和他的同事Thomas Piantanida在Science上发表了一篇论文，声称这种看法是可能的。他们在1983年的论文“在看见红绿蓝黄色”时声称志愿者观看相邻的红色和绿色条纹可能会看到红绿色，而相邻的黄色和蓝色条纹的观众可能会看到淡黄色的蓝色。研究人员使用眼动仪将图像保持在相对于志愿者眼睛的固定位置，因此视网膜细胞不断被相同条纹刺激。例如，一个锥体可能总是看到一个黄色条纹，而另一个锥体总是会看到一个蓝色条纹。志愿者报告说，条纹之间的边界互相褪色，界面的颜色是他们以前从未见过的颜色 – 同时呈现红色和绿色，或同时呈现蓝色和黄色。已经报道了类似的现象，其中字形颜色联觉的人。在颜色合成中，观看者可能会看到不同的字母字符具有相反的颜色。字母“of”的红色“o”和绿色“f”可能会在字母的边缘产生红绿色。
While you can’t ordinarily see both red and green or both blue and yellow, visual scientist Hewitt Crane and his colleague Thomas Piantanida published a paper in Science claiming such perception was possible. In their 1983 paper “On Seeing Reddish Green and Yellowish Blue” they claimed volunteers viewing adjacent red and green stripes could see reddish green, while viewers of adjacent yellow and blue stripes could see yellowish blue. The researchers used an eye tracker to hold the images in a fixed position relative to the volunteer’s eyes so retinal cells were constantly stimulated by the same stripe. For example, one cone might always see either a yellow stripe, while another cone would always see a blue stripe. The volunteers reported the borders between the stripes faded into each other and that the color of the interface was a color they had never seen before — simultaneous red and green or both blue and yellow. A similar phenomenon has been reported in which persons with grapheme color synesthesia. In color synthesthesia, a viewer may see different letters of words as having opposing colors. A red “o” and green “f” of the word “of” may produce reddish green at the edges of the letters.