Greens that stay clean: a twenty-one square mixing study
Green is the colour people most often describe as 'hard' in watercolour, and the reason is almost always the same: the yellow or the blue they are using is a convenience mixture that already contains the third colour. This study isolates the variable.
Sap green — Warm, olive-leaning foliage green.
| Pigment | Parts | Hex |
|---|---|---|
| Winsor Yellow Deep | 4 : 10 (40%) | #D9A02B |
| Cobalt Blue | 3 : 10 (30%) | #3B6FA8 |
| Viridian | 2 : 10 (20%) | #3F7A4E |
| Perylene Maroon | 1 : 10 (10%) | #7B3A38 |
Mixing notes
| Chartreuse Viridian rather than blue keeps this luminous; blue at this ratio would grey it. | 5 yellow + 1 viridian | #B7C243 |
| Summer leaf The most stable green on the palette. It can be diluted to 5% and still read green rather than grey. | 3 yellow + 2 cobalt | #5F8A34 |
| Shadow leaf A staining red is the correct darkener for foliage; a black would kill the green completely. | 2 summer leaf + 1 perylene maroon | #3C5B33 |
| Blue spruce Both pigments are cool and granulating, so this mix separates slightly on the paper — which is what makes conifers look dusty. | 3 viridian + 1 cobalt | #2F5B57 |
| Autumn olive The red here is doing value work, not colour work. Add it last and slowly or the mix turns brown. | 3 yellow + 1 cobalt + 1 perylene maroon | #7A7434 |
- Paint a 30 x 20 cm grid of twenty-one squares. Reserve the left half for two-pigment greens and the right half for three-pigment greens.
- Fix the yellow at four parts throughout the left half and vary the blue from one to four parts in half-parts. Paint in a single flat wash per square.
- Repeat the row with viridian in place of cobalt. Compare the two rows side by side while both are wet, then again when dry.
- In the right half, take your three favourite two-pigment greens and add perylene maroon at one-eighth, one-quarter and one-half part.
- Mark the square where each green stops being green and starts being brown. That boundary is the useful piece of information on the whole sheet.
- Check every square under a daylight lamp. Tungsten light makes viridian look bluer than it is.
- Label the ratios with a waterproof pen. This sheet will be handled for years.
Two pigments, no exceptions
A clean green needs exactly two pigments, one yellow and one blue, both single-pigment. The moment a third is present — even in a small percentage, as in sap green or hooker's green — the mix has a ceiling on its chroma, and no amount of ratio adjustment will lift it.
Winsor yellow deep is a single-pigment warm yellow. Cobalt blue and viridian are both single-pigment. That is why this palette can produce twenty-one distinct greens from four tubes while a twelve-tube landscape set often produces about nine.
Viridian and cobalt are not interchangeable
At four parts yellow to one part blue, cobalt gives a warm olive and viridian gives a bright chartreuse. The difference is not merely hue; viridian is transparent and cobalt is semi-opaque, so the viridian row stays luminous at high dilution while the cobalt row turns chalky below about 10% pigment load.
The practical consequence: for distance greens and thin glazes, use viridian. For solid mid-value foliage, use cobalt. The two rows on the study sheet exist to make that choice obvious rather than remembered.
The darkener problem
Most painters darken green with black, and most green shadows look dead as a result. Black is a neutral, so it desaturates toward grey; a foliage shadow in reality is a cooler, deeper green, not a grey one.
Perylene maroon is the correct tool because it is a deep, transparent, staining red that sits almost opposite green on the wheel. Added at an eighth of a part it deepens without desaturating. Past half a part it starts to neutralise, and that boundary is worth marking on the sheet — it is usually much further than people expect.
What matters
- A clean green needs exactly two single-pigment colours; convenience mixtures cap the chroma.
- Viridian for thin distance glazes, cobalt for solid mid-value foliage — not interchangeable.
- Darken green with a transparent staining red, never with black.
- Perylene maroon stays useful up to about half a part per three parts green — further than most painters assume.
Handling note — Technique notes only. Perylene and viridian are staining pigments that bond with the paper; follow the manufacturer's safety data sheet for handling and disposal.