If humans only have three kinds of color photo-receptors, how can we see so many different colors?

Because our eyes mix the colors together, making new ones. (Purple,green, orange.) the rest of the colors depend on the light. So the light and receptors play a roll into seeing different colors.

answer and explanation;

composition refers to both the types of minerals within a rock and the overall chemical makeup of the rock while texture refers to the size and arrangement of the minerals or grains that make up a rock. both composition and texture can be used to classify rocks, such as igneous rocks. texture describes how the rock became solid or crystallized from liquid, melted rock. composition of a rock describes the minerals that make up a particular rock.