They are most likely to be noticed if they are yellow-green. That is where the eye is most sensitive. Tennis balls are yellow green so that they match the color to which we are most sensitive. We see not only yellow green, but also red and blue. All together, they mix to produce the white light we see.
Red cloth appears red in sunlight, and red by the illumination of the red light from a neon tube.
But because the red cloth absorbs cyan light, it appears black when illuminated by cyan light. A piece of paper that appears white in sunlight has the property of reflecting any color that is incident upon it. The color that will emerge from a lamp coated to absorb yellow is blue, the complemen-tary color. If the yellow clothes of stage performers are illuminated with a complementary blue light, they will appear black. The overlapping blue and yellow beams will produce white light.