The short answer depends on which primaries you use
There are three sets of primary colors in common use, and blue plays a different role in each:
| System | Primaries | Is blue a mix? |
|---|---|---|
| Traditional paint (RYB) | Red, yellow, blue | No, blue is a primary |
| Printing (CMY) | Cyan, magenta, yellow | Yes: cyan + magenta |
| Light on screens (RGB) | Red, green, blue | No, blue is a primary |
So if you are holding a basic red, yellow and blue paint set, nothing in it will make blue. Red and yellow only ever give oranges, and yellow added to blue makes green. If you have cyan and magenta, though, you can mix a perfectly good blue.
Mixing blue from cyan and magenta
Cyan absorbs red light and magenta absorbs green, so a layer of both leaves mainly blue. The ratio matters:
- 2 cyan : 1 magenta gives #505EC1, a mid blue, and the closest to a "true" blue in our tests.
- 3 cyan : 1 magenta gives #4873CC, a lighter cornflower.
- 1 : 1 drifts to #5841A6, already a blue-violet.
The mixed blue is a little duller than a tube of ultramarine or phthalo. Mixing always loses some saturation, because each pigment absorbs part of the light the other one reflects.
Light blue, navy and teal
Once you have any blue, the variations are easy:
- Light blue: add white. 1 part primary blue to 3 parts white gives #C1DCFA, a soft sky blue. Phthalo blue is so strong that the same ratio is still fairly saturated (#B6DFF0), so use much more white with it.
- Navy: add black or a dark brown. 2 parts ultramarine to 1 part black gives #283C6B. Burnt umber instead of black gives a warmer, more natural navy.
- Teal or petrol: add a little green. A third of a part of green to one part blue gives #134E92; more green moves it toward teal.
Choosing a blue paint
Since you usually cannot mix blue, it pays to buy the right one:
- Ultramarine leans toward violet. It mixes good purples and duller, olive greens. It was once ground from lapis lazuli; the synthetic version has been made since the 1820s.
- Phthalo blue leans toward green and is extremely strong. It mixes clean greens and turquoise.
- Cerulean and cobalt are softer sky blues.
Painters often keep one warm and one cool blue for that reason.
Blue on screens
In RGB, blue is one of the three channels, so #0000FF is pure blue light. You can't make it from red and green light. To find a precise blue HEX code, see shades of blue. To see how a screen blue prints, convert it with RGB to CMYK: a bright screen blue often falls outside what CMYK ink can print and comes out duller.
Cobalt and steel blue
| Shade | Recipe in parts | Result |
|---|---|---|
| Cobalt | 2 ultramarine, 1 cyan | #1E55BC |
| Steel blue | 1 ultramarine, ½ burnt umber, 1 white | #889FBC |
Cobalt is ultramarine nudged toward green, which is why one part of cyan does the job. Steel blue shows the effect of a neutralizer: burnt umber is orange-brown, blue's complement, so half a part grays the blue without making it darker the way black would.
Blue icing that doesn't turn green
Buttercream made with butter is pale yellow, and yellow plus blue is green. That's why blue frosting often comes out teal. Two fixes work: beat the buttercream longer so it whitens, or add the smallest dot of violet gel to cancel the yellow before you add blue. Royal icing and shortening-based frostings start white and take blue without the problem.
In acrylics and gouache, a blue that looks too bright straight from the tube is usually tamed best with a touch of its complement, as in the steel blue above, rather than with gray.
FAQ
What two colors make blue?
Cyan and magenta, in roughly a 2 to 1 ratio. With traditional red, yellow and blue paint, no two colors make blue.
Can green and purple make blue?
They get close. Green and purple both contain blue, so mixing them gives a dull blue or blue-gray rather than a bright one.
What colors make dark blue?
Blue with a little black, burnt umber or a darker blue such as Prussian blue. Add the dark color slowly; black overpowers blue quickly.