Exactly, because we haven't seen real non-avian dinosaurs, we should actually make the effort to use what we do know. Like all lines of dinosaurs, except sauropods, have had inferences of feathers in some way,shape, and form. Pterosaurs had fuzz. And Crocodiles have genes for feathers. We also know that the scutes on the feet of birds are actually a kind of modified feather as well. We also know the coloration for several dinosaurs, like sinosauropteryx, sinornithosaurus, Microraptor, anchiornis, and we know that one kind of archeopteryx has at least one black feather, and we may know the pattern for a few non-feathered dinosaurs. We also know that multiple marine reptiles (Read: Ichtyosaurs) were dark or black. All of which blows my mind. We won't know everything about dinosaurs, for every dinosaur we know, there's probably a hundred more that we don't, but I think it's always best to take and use what we know, and draw and build these wonderful creatures as best we can.