Additive Color Mixer

The additive color mixer combines two colors the way emitted light does, summing their red, green and blue channels to show the additive rgb mixing result of overlapping light sources.

What is Additive Color Mixer?

• The additive color mixer combines two colors by adding their channels, which is how light behaves when two beams overlap.
• You choose two colors and the tool adds the red values together, the green values together and the blue values together, clamping each sum at the maximum of 255.
• The result is the color you would see where two spotlights of those colors overlap on a dark stage, or how two glowing pixels would combine if their energy were additive.

This is the model behind every screen. A display draws red, green and blue subpixels, and the viewer's eye integrates their light, so the browser rendering two overlapping translucent colored layers in the additive family behaves the way this tool predicts. Red plus green produces yellow, green plus blue produces cyan, and blue plus red produces magenta, all of which surprise people who are used to thinking in paint. The clamping at 255 is what keeps the sums inside the displayable range: once a channel is already at maximum, adding more light cannot brighten it further.

It is deliberately the opposite of the subtractive colour mixer in this same section, which multiplies channels instead. Additive mixing describes emitters such as screens, projectors, LEDs and stage lights. Subtractive mixing describes pigments, inks and filters, where each layer removes light rather than contributing it. Knowing which model applies is the single biggest source of confusion when people compare a printed proof against an on-screen design, and the two tools exist to make that distinction concrete.

• A useful property of additive mixing is that it can only brighten.
• Because every operation is a sum, the result is always at least as bright as the brighter input in each channel, and the mixed color can never be darker than either source.
• That makes the tool a fast sanity check: if a proposed blend needs to come out darker, additive mixing cannot be the right model and you want the subtractive mixer or a weighted blend instead.

For practical work, additive mixing is the correct mental model for glow effects, light leaks, particle systems, and layered emissive UI elements. It is not a substitute for a designer-grade colour picker with alpha compositing, which weights the blend rather than simply summing it. When you want to know what two lights produce, or want to confirm that a red and green additive pair will read as yellow rather than brown, this is the calculator to reach for.

As an additive color calculator it is also a quick way to check a plan before building it. If you want to mix light colors together in a glow layer, a projector overlap or a set of emissive indicators, check the arithmetic here first: the addition of channels tells you immediately whether a pair will read as a distinct third hue or dissolve into white. The same additive rgb mixing model explains why overlapping translucent screens brighten toward white in the middle, which is a common surprise when stacking luminous overlays without controlling their combined intensity.

How to use Additive Color Mixer

1. Set Light A and Light B.
2. Read the sum: each channel is added and clamped at two hundred and fifty-five.
3. Compare the result with the two inputs — additive mixing is the mental model for glow and projection, not for pigment.
4. Use the subtractive mixer when the two colours are inks or filters rather than lights.

When to use Additive Color Mixer vs related tools

Use additive mixing for anything that emits light: screens, LEDs, projectors, stage lighting and emissive glow effects. Switch to the subtractive mixer for pigments and inks, and to the two-color blend tool when you want a weighted interpolation rather than a pure sum. The subtractive mixer is the pigment-side counterpart, and the CMYK channel mixer exposes the four ink channels directly.

Privacy & Security

This tool runs entirely in your browser — no data ever leaves your device. There is no server round-trip, no upload, no logging, and no account required. Your input is processed locally using client-side JavaScript and is never stored, transmitted, or accessible to anyone else. When you close the tab, everything disappears.

Frequently asked questions about Additive Color Mixer