Hair Colour Theory

Colorimetry is the theory layer that makes the rest of the Academy predictable. Read these pages once properly and the formulas stop looking arbitrary: you will understand why a level seven with warm reflects behaves differently from a level seven with ash, why undertone exposed by lightening needs pre-pigmenting, and how the colour wheel maps onto the tube numbers on your shelf.

We cover the fundamentals — the level system, tone direction, warm, neutral and cool balance, complementary neutralisation, and how porosity changes everything — in plain language with the professional vocabulary kept intact, because you need the real terms when you are talking to a client or a brand rep.

Each concept links forward to the formulas and techniques that apply it, so theory never floats free of practice. This is the section to hand a new assistant, and the section to re-read when a correction goes sideways and you want to know precisely why. It is also the shortest route to explaining to a client why their desired shade takes two visits.