Blue and yellow are the two colors traditionally mixed to make green. That's the simple, textbook answer most people learn in school. But the full picture depends on what kind of "mixing" you're talking about, because color mixing works differently for paint than it does for light. Here's the breakdown.
1. Paint, ink, and pigments (subtractive mixing)
When you mix physical colors — paint, ink, dye — you're doing subtractive mixing.
Each pigment absorbs (subtracts) certain wavelengths of light and reflects the rest.
Mix blue and yellow paint, and the result absorbs most wavelengths except green, so green is what reflects back to your eye.
This is the traditional "primary colors" model taught in art class: red, yellow, and blue are primaries, and green comes from mixing two of them (blue + yellow).
2. Light (additive mixing)
If you're mixing colored light — like on a screen or in stage lighting — the rules are different. This is additive mixing.
The primary colors of light are red, green, and blue (RGB).
In additive mixing, green isn't made by combining two other colors — it's already one of the three primaries.
Mixing red light and green light gives yellow. Mixing all three (red, green, blue) gives white.
So on your phone or TV screen, green pixels are literally just green — they're not created by blending anything.
3. The more accurate pigment model (CMY)
Modern color theory, especially in printing, uses cyan, magenta, and yellow as primaries instead of red, blue, and yellow.
In this system, green is made by mixing cyan and yellow, not blue and yellow.
This is technically more accurate than the old red-yellow-blue model, because cyan and yellow are closer to true subtractive primaries. Your printer uses CMYK (cyan, magenta, yellow, black) for exactly this reason.
So which answer is "correct"?
If you're talking about paint in a school-level, everyday context: blue and yellow is the standard and expected answer.
If you're talking about precise color science or printing: cyan and yellow is more accurate.
If you're talking about light or screens: green isn't mixed from other colors at all — it's a primary.
A quick practical note
The exact shade of green you get from blue and yellow paint depends heavily on which blue and which yellow you use. A cool blue (like phthalo blue) and a warm yellow will give a different green than, say, ultramarine blue and lemon yellow.
This is why "blue + yellow = green" is true as a general rule but not a precise formula — real-world pigments aren't pure, so results vary.
Bottom line
Paint/pigments: blue + yellow (traditional) or cyan + yellow (more precise).
Light: green is already a primary color, not a mix.
Context matters more than most people realize — the "right" answer changes depending on whether you're painting, printing, or looking at a screen.