Why don't colored pencils erase?
For grown-ups: the science
Colored pencil color gets into the paper's bumps and gaps, so an eraser has a hard time taking it away.
Most colored pencils use cores made by holding color materials, such as pigments or dyes, together with wax, oil, or resin. Pressure pushes the color and binding materials into the paper's fibers and bumps, making them hard to remove with an eraser. Erasable colored pencils adjust the binding materials so they can be removed more easily.
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Transcript
When you color a picture and rub it with an eraser, why doesn't the color disappear?
Colored pencil leads are made of color powder and wax. The color gets caught tightly in the paper's bumps.
Erasers grab the black powder from pencil marks. But waxy color stays in the paper's tiny gaps.
The harder you color, the more the color is pressed into the paper. So even an eraser cannot easily get it all off.
Colored pencil color stays in the paper's tiny gaps, so it is hard to erase.