(Post Production) Colour grading is where an editor or specialist colourist will manipulate the colours to match shots or stylise footage. When films are shot, it's extremely rare that all of the footage is filmed in exactly the same location, on the same day, at the same time of day, with the same lighting conditions, so the job of the editor/colourist is to ensure that the colour of the shots, given all these variables remains consistent and then is embellished as the production design dictates.