system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how did they know the colors of dinosaurs?
gpt
For the most part we don't.

This is the reason why some iconic dinosaurs are depicted with different colors in every picture we make of them. Google images of T-rex and you will find a wide variety of colors, skin textures, feathers and poses.

Artist depiction of dinosaurs are mostly guesses based on what living creatures with similar lifestyle and habitats look like. 

Originally dino images where colored based on what living reptiles may have in the way of colors and the idea that camouflage and blending in the background is common among predator and prey. More modern images have more bird-like features.

For a few rare cases we have some bits of skin or feathers, but that mostly gives us some hints as to textures and not necessarily color.