Slightly on topic. Very slightly.
I'm watching a Muse (the band) live concert on tv and during a song this banker comes on stage and throws away worthless dollar bills to the audience. Or whatever the message is.
Anyway, this specific clip is in b/w but the notes he throws away are brightly coloured.
I realize this is probably the most simple effect nowadays but someone explain to me how they do that with moving objects without having to add the colour frame by frame.