When reality isn't real enough it becomes aesthetically necessary to make it more real through artificial means.
In film making, there are times when real rocks are removed from the set and replaced with styrofoam replicas because the real rocks just didn't look right. The color was all wrong. The shape was inconsistent with the crew's expectations for rocks. Reality simply is not dependable enough.
After all, they do paint oranges orange because people want their oranges to be orange.
So, you've just purchased a rock and you want to show it to your friends. Be wary. If your rock does not look like what they think a rock should look like they will not be impressed. Going to use the rock as a centerpiece during dinner? Splurge and buy some rock colored paint and paint that baby the right colors. No use risking dinner conversation taking terrible tangents when your guests question the veracity of your rock.
Quiet on the set. Makeup! Your complexion is too pale. We need to paint it to make it look like real skin.
Building a model? Designing a set? Selling food products to the general population? Serving a refreshing beverage to a distinguished clientele? You might wish to consider stocking up on paints, dyes and colorings. People don't care for dull, murky liquids and foods that lack a jazzy, glowing color. In an advanced civilization there is no room for error. If the real thing just doesn't look real enough you'll need to paint that rock to make it look more like a rock. Reality has never been so tenuous.