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Colour on Stage: RGBW, CMY, Colour Temperature and CRI
Why two white fixtures do not match, what the extra emitters in a hex fixture are for, and the number that decides whether skin looks right.
~8 min read · Updated August 2026 · By the Stage Supply team
In this guide:Additive mixing · Colour temperature · CRI · In practice · Picks · FAQ
Colour is the part of lighting that looks simplest and behaves least predictably. Two fixtures that both claim white will not match. A saturated blue that looks superb on a backdrop makes a face look ill. A cheap fixture and an expensive one can put out the same lumens and look completely different on a costume.
The reasons are all in how the colour is made.
How LED colour mixing works
Stage LEDs mix additively: separate coloured emitters combine to make the colour you see. Start with red, green and blue and you can reach a wide range, which is why RGB was the first generation.
The problem with RGB is white. Mixing red, green and blue to make white gives a white that is technically white and looks wrong on skin, because the spectrum has gaps. That is why extra emitters exist.
| Configuration | Emitters | What the extra one buys |
|---|---|---|
| RGB | Red, green, blue | The basics, poor whites |
| RGBW | Plus white | A usable white and better pastels |
| RGBA | Plus amber | Warmer whites, better skin tones |
| RGBAW | Plus amber and white | Wide range, good warm whites |
| Hex, RGBWAUV or similar | Plus amber, warm white or UV | Widest range, including UV effects |
| CMY | Subtractive, on moving heads with a lamp | Continuous mixing rather than steps |
More emitters means better whites and better pastels, and it also means a higher price and slightly lower output per watt, because not every emitter is on for every colour.
Colour temperature, and why whites clash
White is not one thing. Colour temperature, measured in kelvin, describes where on the warm to cool scale a white sits.
- Around 2700 to 3200 K is warm white, similar to tungsten. Flattering on skin, traditional for theatre.
- Around 4000 K is neutral.
- Around 5600 to 6500 K is daylight, cool and blue by comparison, and what cameras usually expect.
The practical problem is mixing. A warm white front light next to a daylight white front light looks like a mistake, because the eye is very good at spotting the difference side by side. Buy white fixtures for one job in one colour temperature, or buy variable white fixtures and set them to match.
If anything is being filmed
Cameras are less forgiving than eyes. Mixed colour temperatures that look acceptable in the room can look badly wrong on camera, and white balance can only correct for one of them.
CRI, and why cheap white looks wrong
Colour Rendering Index is a measure of how accurately a light source shows colours compared to a reference. It runs to 100, and higher is better.
- Below 80 is poor. Reds go brown, skin looks grey, and costume colours are not what the designer chose.
- 80 to 90 is acceptable for general use.
- Above 90 is what you want on faces, and fixtures aimed at theatre and broadcast quote it prominently.
CRI has known limitations, particularly on saturated reds, and newer metrics such as TM-30 give a fuller picture. For buying purposes the rule holds: for anything lighting people, especially on camera, high CRI is worth paying for. For a colour wash on a wall it matters much less.
Practical rules
- Use high CRI, warm or variable white fixtures on faces. Save the colour-mixing fixtures for the wash and back light layers.
- Buy in matched sets. Two fixtures from different batches can differ visibly, and different models certainly will.
- Check the white by eye before the client does, on a white surface, side by side.
- Saturated colour hides differences, pastels expose them. A pale lavender wash is the hardest thing to match.
- For UV effects you need a fixture with a genuine UV emitter, not a blue one, and 365 to 395 nm is the useful range.
Fixture choice by family is in fixture types, and where each layer goes is in lighting a stage.
Popular picks from the shop
Frequently asked questions
What is the difference between RGBW and RGBA?
The fourth emitter. RGBW adds white for cleaner whites and pastels. RGBA adds amber, which gives warmer whites and generally better skin tones. Hex fixtures include both plus more.
What CRI do I need?
Above 90 for anything lighting faces, particularly on camera. Above 80 is acceptable for general washes. Below 80 will make skin and costume look wrong.
Why do my two white fixtures look different?
Different colour temperature, different emitter mix, or different production batches. Whites are the hardest thing to match, which is why matched sets and variable white fixtures exist.
Can I get true white from an RGB fixture?
You can get something the meter calls white, but the spectrum has gaps, so skin and fabrics render poorly. If white matters, buy a fixture with a dedicated white or amber emitter.
