Monitor Color Test

Run the color test

1. Pick one of the 11 preset colors, or set your own under Custom color: drag the Red, Green and Blue sliders, type a code such as #1a2b3c or #abc in the Hex box, or use Pick.
2. Press Start test, click or tap the preview, or press F, to fill the screen.
3. Step through the presets with Next and Previous, the Left and Right arrow keys, Space, Enter or a tap. After a custom color, they continue from the last preset used.
4. Look for areas that seem darker, lighter or a different shade, and for a color that looks off, such as red that looks orange.
5. If a color looks wrong, try another picture mode or color temperature in the display's own menu and look again. The page has no brightness or picture controls of its own.
6. Press Esc or Exit when you are done.

What is a screen color test?

A screen color test fills the display with one solid color at a time so you can judge how it shows each one. Pure red, green and blue each use one channel of the signal on its own, so a problem with that channel stands out; white and grays mix all three and reveal tint. It is a visual check, not a measurement of color accuracy.

What tint and patches look like

A tint is an even cast over the whole screen: white looks cream or yellow, bluish or pink, and grays share the same cast. A patch is an area that looks darker, lighter or a different shade from the rest, often in a corner or along an edge, and stays in the same place on every color.

A tint that covers the whole screen evenly usually comes from a setting. A tint in one area only points to the panel, which the Screen Uniformity Test checks. For an even tint, look at these first:

• Night light, Night Shift, True Tone or a blue-light filter, which warm or adjust white on purpose.
• A warm color temperature, or a reading or low-blue-light mode, in the monitor's own menu.
• The color profile in your operating system's display settings.
• A loose or damaged cable or connector, especially if the tint changes when you move it.

Calibrated vs uncalibrated

A calibrated screen has been measured with a colorimeter and corrected with a color profile, so its colors match a target such as sRGB. An uncalibrated screen shows colors the way its factory settings and picture mode make them, which can still look fine to the eye.

A website cannot calibrate or check color accuracy. Color accuracy means how closely the light your screen gives off matches the color it was sent. Checking it takes a colorimeter, a sensor placed on the screen that reads a series of patches; calibration software compares the readings with their targets, reports the error as Delta E and writes a correction profile. A web page never sees the light your screen emits, and your eyes adjust to whatever white is in front of them.

You can still set brightness, contrast, gamma and white balance by eye. The guide to calibrating a monitor without a colorimeter explains the steps and what only the sensor can do.

What this test can detect

• A primary that looks off, such as red that looks orange or blue that looks purple.
• An even cast over the whole screen, such as white that looks yellow, blue or pink.
• Patches or edges in a different shade from the center.
• Grays that do not look equally neutral from dark to light.
• A dot that stays one color while the rest of the screen changes.

How it works

The page paints the test area with a plain CSS background: the #rrggbb value of the current color, one of 16,777,216. The 11 presets are Black, White, Red, Green, Blue, Yellow, Cyan and Magenta at full values, then Gray 50% (#808080), Gray 25% (#404040) and Gray 75% (#bfbfbf). The label on the preview names the preset and its code, such as Red · #ff0000, or shows the code alone for a custom color.

Start test asks the browser's Fullscreen API to fill the screen, with a fixed overlay where it is not available. The controls and pointer hide after 2.5 seconds without input. Nothing is measured.