Colour grading
Also said as LUT, Lookup table, Post-processing colour
Shifting all the colours of the finished picture to set a mood, as a last step. A LUT, or lookup table, stores the shift as a small cube of colours: each input colour simply looks up its output.
One small image can change the whole mood of a level, cheaply, at any time, and can be crossfaded with another. It can also flatten your careful value work if pushed too far.
Say it
“Grade the flashback with a LUT: lift the blacks, pull saturation down 30%, push shadows towards teal. Crossfade it in over two seconds rather than cutting.”
Where you’ve seen it
Fallout 3's wasteland has a green cast that players still argue about, and mods such as Fellout exist to remove it. Fallout: New Vegas went warm, with browns and oranges, so the two games feel apart at a glance.
Not to be confused with tone mapping
Tone mapping squeezes bright light into the range a screen can show. Grading then chooses the look. Tone mapping is usually a technical step and grading a creative one.