Black is all pigments. It is the absence of color.
Yup. But light is the complete opposite as pigment. Add all colors together to get white. Remove all light and you get black.
When I was young, that confused me a bit.
You can truthfully say that light is both the presense of all colors and the absence of all colors. Just depends upon what you are talking about.
The best explanation I could ever come up with to explain it to students was that a color seen from a pigment is actually what it "rejects." It absorbs everything else. Something that's black absorbs all colors; That it means it absorbs "all the white." There is nothing to reflect, so it appears black. A red dress actually isn't red -- it's everything but red.