Screen Color Test

What this screen colour test checks

A screen can have every pixel working and still show poor colours: a white that looks yellow, skies that break into stripes, dark scenes where nothing can be made out. Most of the time a setting is the cause, not the panel.

This test shows six full-screen pictures and asks one precise question about each:

• Tint. Is white really white?
• Gradients. Do tones change smoothly, or in visible bands?
• Darkest tones. How many near-black squares can you tell apart from black?
• Brightest tones. How many near-white squares can you tell apart from white?
• Gamma. Are mid-tones as bright as they should be?
• Wide colours. Does your screen really show colours beyond the standard range?

Each answer gets a plain result, with what to change when something is off. You can also fill the screen with any colour you choose. Nothing is installed and nothing leaves your browser.

Before you start

• Turn off night light, “eye comfort” and blue-light filters: they tint the whole picture on purpose.
• Use your normal brightness, and let the screen warm up for a few minutes.
• Look at the screen straight on, without direct light falling on it. Reflections hide the darkest tones.

How to use it

1. Press Start the check. The screen goes full screen.
2. On each step, read the short description, look at the picture, then press your answer.
3. Go to the next step with the arrow, the right arrow key, Space or a swipe. You can skip a step.
4. Press Finish. Your six results appear, with a link you can keep or send.

To leave at any time, press Esc or the cross. Your answers are kept, and the button becomes “Continue the check”.

How to read your results

Tint

White should look neutral. The eye adapts to a tint in a few seconds, so compare with a sheet of white paper in daylight, or with another screen.

• Yellow or orange: a night light or a “warm” or “reading” picture mode is active.
• Blue: common on new screens. Choose “Warm” or “6500K” as the colour temperature in the monitor’s menu.
• Green or pink: a colour setting, a colour profile, or on an external monitor a loose or damaged cable.

Gradients

Each ramp goes from black to a full colour in 256 levels. On a good screen it looks continuous, or shows very fine, regular steps. Wide bands mean that fewer levels are displayed than there should be. Usual causes are a colour depth set too low, a “limited” output range, a picture mode that boosts contrast, or a remote desktop or screen-sharing program that compresses the picture.

Darkest and brightest tones

Ten squares differ from the background by 1% to 10%. Counting how many you can see tells whether detail survives at both ends.

• 8 to 10: detail is kept.
• 5 to 7: the last tones merge with the background. That is common and often comes from the room: a bright room hides dark squares.
• Fewer than 5: detail is lost. For dark tones, raise the brightness or the “black level” setting. For bright tones, lower the contrast.

On a computer connected by HDMI, a mismatch between “Full” and “Limited” output range is a classic cause: both the computer and the screen must use the same one.

Gamma

Gamma describes how bright the mid-tones are between black and white. The standard value is 2.2. In the picture, fine black and white lines send out exactly half the light of white. The grey square that looks as bright as the lines tells the gamma of your screen. Step back, or half close your eyes, until the lines blend into a grey.

• 2.2: the standard. Pictures have the contrast their authors intended.
• 2.0 or 2.4: close. 2.4 is often chosen for dark rooms.
• 1.8 or 2.6: mid-tones are clearly too light or too dark. Look for a “Gamma” setting, or try another picture mode.
• None: the lines are blurred before they reach the screen. Check the native resolution with the screen resolution test.

Wide colours

Ordinary screens show the standard range of colours, called sRGB. Wide-colour screens (often labelled P3) show stronger reds and greens. The picture uses the strongest standard red and green, with a disc of the strongest wide-colour red and green inside.

• You see the discs: wide colours are really displayed.
• You see no disc: your screen shows the standard range, which is the case for most screens, or the wide colours are not passed on by the system or the browser.

The result also tells what your browser declares about the screen: its colour range, and whether HDR is active.

Show a colour full screen

Choose a colour with the picker, type its code, or press a quick colour, then “Show full screen”. A tap or a click hides the controls so that the colour covers the whole screen.

People use it to check how a brand colour looks on a given screen, to see dust and smears before cleaning (black or white work best), to compare the tint of two screens side by side, or as a plain light.

What a browser cannot tell you

This is a visual check: every result is what you reported. A web page cannot measure the light coming out of a screen. It cannot tell how accurate the colours are, give a “Delta E” figure, or calibrate anything. Real calibration needs a measuring device placed on the screen, called a colorimeter, and its software.

What this test does well is finding the settings that spoil a picture: a filter left on, a wrong range, a crushed black level, a wrong gamma. Fixing those brings most screens close to what they can do.

Troubleshooting

Colours look dull or grey with HDR on

On Windows, switching HDR on changes how ordinary content is displayed, and the desktop often looks washed out. Run the check with HDR off, then with HDR on, and compare the two results.

Blacks look grey

On an LCD screen, black is never fully dark: the backlight shines through. If black is clearly grey, check the “black level” or “HDMI range” setting, which must match on the computer and on the screen.

I see bands only in one colour

Bands in a single ramp point to a colour setting for that channel, or to a colour profile. Reset the monitor’s picture settings, and in the system remove any custom colour profile.

The picture changes when I move my head

That is the viewing angle of the panel, not a colour fault. Judge the pictures from straight on.

Frequently asked questions

Is anything recorded or sent to TestrHub?

No. The pictures are drawn by the page in your browser and your answers stay there. Saved results stay in your browser, and a result is only shared if you copy its link.

Is this a calibration?

No. It finds visible problems and wrong settings. It does not measure colours and cannot replace a colorimeter.

What are sRGB, P3 and HDR?

sRGB is the standard range of colours that all screens and websites share. P3 is a wider range, with stronger reds and greens, found on many recent phones and laptops. HDR is about brightness: much brighter highlights next to deep blacks.

Why is my white yellow in the evening?

Phones and computers warm the colours after sunset to reduce blue light. The setting is called Night Light, Night Shift or Eye Comfort. It is harmless, and you should turn it off for this test.

Why do the fine lines in the gamma step shimmer?

One-pixel lines are at the limit of what a screen can show. A slight shimmer when you move is normal. Strong waves mean that the picture is rescaled.

Which test should I run next?

The dead pixel test looks for faulty pixels with solid colours, and the screen test checks uniformity, backlight bleed and motion.