Color theory
Complementary colors, as they behave in the tube.
By Marco, painter and founder of chromilla ยท Last checked August 2026
On a screen, complements cancel to a neutral gray. On a palette they rarely land there, because tinting strength differs wildly between pigments and most tubes are not sitting exactly opposite each other. Below are five pairs painters really use, with the whole neutralising ladder computed from pigment data.
The neutralising ladders
Left is pure first tube, right is pure second tube. The grays in the middle are the useful part. Select a pair to read the notes.
Cadmium Red and Phthalo Green
The classic red and green pair. Phthalo is very strong, so start with a speck of it.
- 100% Cadmium Red / 0% Phthalo Green = #E62B1E
- 85% Cadmium Red / 15% Phthalo Green = #372C1E
- 70% Cadmium Red / 30% Phthalo Green = #252D1F
- 50% Cadmium Red / 50% Phthalo Green = #192F21
- 30% Cadmium Red / 70% Phthalo Green = #123323
- 15% Cadmium Red / 85% Phthalo Green = #0E3826
- 0% Cadmium Red / 100% Phthalo Green = #0A412A
Four things the diagrams miss
Equal parts is almost never equal effect. Phthalo green has several times the tinting strength of cadmium red. A visually balanced neutral often sits nearer 85% red to 15% green.
Complements gray down, black flattens. A mixed neutral keeps a temperature, so it still belongs to the painting. Black drops chroma and value at the same time and reads dead next to a color passage.
Neutrals shift as they dry. Acrylics darken slightly, watercolour lightens. The science page explains how Chromilla models that.
Your tubes are not these tubes. Brand formulations differ. Point the color mixer at your brand and medium to get ratios calibrated to what you actually own.
See every pair at once
The interactive color mixing chart lays out ten tubes against each other in one grid.