"Living pigments" is a metaphorical device to refer to the fact that the pigments of the original paint have been replaced by pigmented micro-organisms.
“活颜料”是个比喻，意味着绘制岩画最初使用的颜料已被画作表面微生物取代。
2
A pigment is the substance that gives an object its color. Grass, apples, hair, and paint, for example, are all pigmented.
色素是赋予物体颜色的物质。比如，草、苹果、头发、颜料都有色素。
3
It doesn't make any common sense at all to apply a pigmented or colored wax on top of a paint that is as clear as the windshield you look through.