Monitor Color Test

A monitor colour test fills the screen with one fully saturated colour at a time so you can judge how faithfully the panel reproduces it. On a well behaved display each field looks pure and even edge to edge. Problems show up as a tint pulling the colour toward another hue, patches that look lighter or darker than the rest, or visible steps where a smooth field should be smooth.

Start with the three primaries. Red, green and blue drive one subpixel channel each, so a primary that looks washed out, orange-ish, or unevenly bright points at that channel specifically. Then move to the secondaries. Cyan, magenta and yellow each mix two channels, which makes them far better at exposing a colour balance problem: a magenta field that leans pink or purple tells you the red and blue channels are not tracking each other, something you would never notice on the primaries alone.

White and black close the test out. White is the most revealing field for a colour cast, because any imbalance between the three channels shows as a warm or cool tint rather than a colour, and it is where a mismatched colour temperature setting becomes obvious. Black shows how deep the panel can actually go, which on an LCD means seeing how much backlight escapes.

Watch for banding while you cycle. If a field shows faint stripes instead of one flat colour, the signal path is quantising somewhere — often a display set to a limited colour depth, an aggressive scaling mode, or a video driver sending a restricted RGB range. That is a settings problem far more often than a panel fault, so it is worth checking the cable, the refresh rate, and the output colour depth before assuming the screen is at fault.

This test shows you what the panel is doing but cannot correct it. Matching colour to a known standard requires a hardware colorimeter; what a full-screen test gives you is a fast way to spot that something is off, and a way to compare two displays side by side.