Ken Lewis, age 12, of Peterborough, Ontario, or s question:

What causes color?

Every colored object copies with the colors of the rainbow. A blue bird sifts out the blue rays and reflects them back. The rainbow colors we do not see are absorbed, or soaked up.

A white lily absorbs no color from light. It bounces back all the colors and we see white, which is the color of ordinary light. The fur of a black cat absorbs all of the colors and reflects none of them back.

The skein of colors in a sunbeam are absorbed or reflected back by certain chemicals. The red rose has chemicals which absorb the blue, yellow and green colors of the rainbow and reflect back the brilliant reds, Chemicals in the feathers of the blue bird absorb the red, yellows and greens and bounce back the blues„

When these chemicals are concentrated we call them pigments. They are strong enough to carry along their color sifting qualities, even when mixed with other chemicals. Lapis lazuli is a lovely blue stone which was once used as a pigment by artists, It kept its lovely color when powered, mixed with oils and used as paint. Even its ashes were used as a pigment, for they have a pinkish color which was used to give delicate flesh tones. Nowadays, these pigments are man‑made from cheaper chemicals.

With a paintbox, we get many colors by mixing. But certain pigments cannot be made by mixing. They are red, blue and yellow, the primary pigment colors. Purples, mauves and violets are made by mixing the primary colors red and blue. Greens are mixtures of blue and yellow; orange is a mixture of red and yellow; and brown is blue and yellow with a touch of red. If we mix the three primary pigments together in a perfect blend we get black.

These chemical colors, however, are not the same as the blue in the sky, the red of a searchlight or the colors of the rainbow ‑ which are the colors of light. These rainbow colors have different primary colors and mix in different blends. The primary colors of light are blue‑violet, yellow‑green and red‑orange. If we remove one of these colors from the rainbow, we cannot possibly mix it from what is left.

We can see how the primary colors of light mix by shining colored beams down onto a white surface. Abeam of red‑orange with a beam of blue‑violet light produces a magenta color. Abeam of blue‑violet with a beam of yellow‑green produces blue. Red‑orange and yellow‑green produce yellow. These primary and mixed colors are the colors of the rainbow, the colors of the spectrum of white light. When the three primary colors of light are all blended together on a white surface, the color is white, dust as in ordinary sunlight the colors of the spectrum are blended together to form white, or colorless light.