It would be great the ability to change the color of a part at a assembly level and if desired make the color change at the part level too using the comand "Push Color to Part".
It happen quite often and if you choose to change a color of a part in all the files (part..subassemblies..main assembly), you have to open the part separately and change the color.
It would be possibile to do that directly from the main assembly file, using if necessary a multiselection too.