Screen Colour Test.
Fill your screen with pure red, green, blue and every secondary colour to judge reproduction, spot a tint or colour cast, and catch stuck sub-pixels — free, in your browser.
How the colour test works
Your screen makes every colour by mixing three light sources in each pixel — red, green and blue sub-pixels. Flooding the whole display with one pure colour at a time is the simplest way to see whether those channels are behaving: a healthy panel shows a flat, even field with no tint, no patchiness and no odd dots.
- 1. Go full screen. Launch the test and let the colour fill the display edge to edge — glare and desktop clutter hide subtle problems.
- 2. Start with white. Pure white should look neutral. A pink, blue or green tinge means a colour cast from the panel or its colour profile.
- 3. Step through the primaries. Red, green and blue each light one channel. Every field should be uniform and fully saturated, with no washed-out or off patches.
- 4. Check the secondaries and edges. Cyan, magenta and yellow confirm channels combine correctly; scan the corners for colour or brightness drop-off.
What your results mean
Compare what you see against a flat, neutral field on every colour — the table below maps the common problem patterns to their cause and the next step.
| What you see | What it means | What to do |
|---|---|---|
| Every colour fills the screen evenly, edge to edge, and white and grey look completely neutral | Your panel reproduces colour accurately, with no cast and no patchiness | Nothing to do. |
| White or the 50% grey field looks pink, green or blue instead of neutral | A colour cast from the panel or its colour profile | Recalibrate your OS display profile, or adjust the monitor's colour temperature / RGB gain — confirm with the colour accuracy test. |
| One area — often a corner or edge — looks a different shade or dimmer than the rest of the same field | Uneven colour or backlight across the panel (clouding, IPS glow or backlight bleed) | Gauge the severity on the uniformity test; if it's severe on a new display, return it while in warranty. |
| A tiny dot that stays the wrong colour on every field, or a black speck on just one pure colour | A stuck or dead subpixel | Isolate the exact channel on the RGB channel test; if it's permanent on a new display, return it while in warranty. |
| Yellow looks orange, or cyan looks washed out | One of the two channels feeding that secondary colour is weaker than the other | Find the weak channel with the RGB channel test. |
What each field tells you
Primaries — red, green, blue
The three colours your screen physically emits. Each pure field lights just one sub-pixel channel, so a weak or dead channel shows as a dull or dark patch, and you can judge whether each one reaches full, even saturation edge to edge.
Secondaries — cyan, magenta, yellow
Made by lighting two primaries at once. They confirm the channels mix correctly and reach full brightness together — if yellow looks orange or cyan looks pale, one of the two channels feeding it is weak.
White & grey — the tint test
Neutrals carry no colour of their own, so any pink, green or blue you see in the white or 50% grey field is a colour cast from the panel or its profile — the fastest way to catch a white-balance problem.
This test is about colour reproduction — tint, saturation and even colour across the panel — not hunting individual bad pixels. To chase a single dead, stuck or hot pixel, use the dead-pixel test; to attribute a fault to one subpixel channel, the RGB channel test. And because a browser can only send reference colours, never measure what your panel emits, this finds obvious faults but is not a substitute for hardware calibration.
Frequently asked questions
What does a screen colour test show?
It floods your whole display with one pure colour at a time. On a healthy panel each field looks flat and even, edge to edge. It reveals a colour cast (a red, green or blue tint), uneven colour or brightness across the panel, banding on solid fills, and any stuck sub-pixels that show the wrong colour.
How do I check for a colour cast or tint?
Open the white and the grey (50%) fields full screen. Pure white should look neutral, not pink, blue or green. If it has a tint, your display or its colour profile is off — try recalibrating in your OS display settings, or adjust the monitor’s colour temperature / RGB gains.
What is the difference between primary and secondary colours here?
The primaries are the three colours your screen actually emits — red, green and blue (RGB). Secondaries (cyan, magenta, yellow) are made by lighting two primaries at full strength. Testing each in turn confirms every sub-pixel channel drives correctly and to full saturation.
Can this calibrate my monitor?
No. A browser can display reference colours but cannot measure what your screen actually emits — that needs a hardware colorimeter. Use this test to spot obvious problems (tints, dead channels, banding); use a calibration device for accurate colour work.
Does it run on a phone, tablet or TV?
Yes — it fills any screen with a browser. Tap or press the arrow keys to move between colours, and use Esc or the back button to exit. On a TV, use the remote’s arrow keys.