You’re a Renaissance artist. You have a very limited range of paint colours. How do you make shadows that aren’t muddy or too dark? Easy: you paint the shadows in a different colour.
Cangiante is the High Renaissance technique of painting shadows in a different hue, for example painting a yellow robe with green shadows. It is used extensively in Michelangelo’s Sistine Chapel paintings to give depth and detail without sacrificing light and vibrancy.