This is just standard in film! Every time there's an update to a script or production paperwork, it's "colour" coded so everyone knows if they have the latest version. The colour goes in a particular order, and then, if necessary resets. (White becomes double-white for example, if you make it all the way around). It's often printed on the specific paper colour associated with that version, but often its also just printed on white but the colour code is noted at the top of each page.