Screens · guide

Monitor blue color problem, and the test that unplugs the computer

By Alberto Gulotta · Updated 18 September 2026 · 15 min read

A monitor blue color problem has two possible homes — the monitor, or everything feeding it — and one test separates them for nothing. Pull the video cable out, leave the power in, and see whether the blue is still there. Everything else on this page depends on that answer.

That correction is worth making before the steps because of where it sends people. The usual advice for a blue cast is a short tour of Windows: night light, accessibility settings, colour management, then the driver. Half of that tour is the right place to look and half of it is the wrong direction, and none of it is worth doing at all on a monitor that is producing the blue by itself. Two minutes with the cable out tells you which of those two situations you are in, and it is the only step here that cannot be wasted.

1. Pull the video cable out of the monitor and leave the power in. This is Dell’s self-test feature check, and what it is for is the whole reason to start here: it “allows you to check if the Dell monitor is functioning properly as a stand-alone device.” With no computer attached, nothing in Windows can be reaching the panel.
2. Run the monitor’s own diagnostic, the one that paints colours. Dell lists the symptoms it is for, and a colour fault is among them: you run it “when you notice screen abnormalities like flickering, distortion, clarity issues, fuzzy or blurry image, horizontal or vertical lines, color fade, distorted image.” The steps are not one key combination — Dell sends you to your own model’s user guide, under Troubleshooting, and notes separately that monitors with a joystick have their own route.
3. If the blue is there in the self-test, reset the monitor before anything else. Every monitor keeps its own colour preset and colour temperature, and those live in the monitor rather than in the computer. Dell documents the way back: the Factory Reset option in the On-Screen Display menu, again per model, in the user guide. It costs nothing and it undoes a preset somebody chose by accident two years ago.
4. If the blue is gone in the self-test, remove the display colour profile. Windows keeps one profile per display and it survives driver updates, which is why updating the driver so often changes nothing. Microsoft documents both halves in the same place: Settings, System, Display, Color profile, then “Remove a color profile” or “Set a default color profile”.
5. Then swap the cable, and the port. A damaged or badly seated cable is the one cause that can sit on either side of the two tests above, because it is not in the monitor and not in Windows. Swapping both is ten minutes and it removes the last thing that is neither.
6. Photograph the screen next to a phone showing the same picture. A cast is hard to judge by memory, and a second screen showing the same picture is the simplest comparison there is. Note the date on it.

The table above is the shape of the whole question. A monitor is not a peripheral that Windows drives: it is a device with its own settings, its own memory of them and its own menu, and the computer can see almost none of it. Microsoft says as much about brightness, which is the setting that looks most like a Windows control and is not one. Colour temperature and colour presets sit in the same place, behind the monitor’s own buttons, and a preset called something like “Cool” will produce a blue cast that no software step on any page will ever reach. That is why the factory reset in the monitor’s own menu comes before the driver and not after it.

One more thing about profiles, because it is where a blue cast most often hides on a machine whose monitor is fine. A colour profile is a file describing how a display renders colour, and Windows keeps one per screen. A wrong one — installed by a monitor utility, carried over from a different display, or written by a calibration that went badly — produces a cast that looks exactly like a hardware fault and is not touched by anything done to the driver, because it is not part of the driver. Removing it is three clicks and it is reversible, which makes it the cheapest thing to try after the self-test. The same trap on a laptop, in green rather than blue, is in how to fix a laptop green screen.

Two neighbouring cases. If the picture is moving rather than tinted — a shiver, a pulse, a flicker at the edge of vision — the test is the same one but the reading is different, and that is monitor flickering. And if part of the monitor has gone dark rather than blue, the fault is not a colour fault at all: a half black screen starts from which of the three built-in tests is yours.

Not covered here. It will not cover a laptop’s own screen. There the cable cannot come out, so the test is a different one and it is in the green-screen page next door.

It will not walk through calibrating a display with a colorimeter. That is a choice about accuracy, not a repair, and it starts after this page ends.

It will not price a panel or a monitor repair. None of the three documents read for this page publishes a figure, and a quote against the price of the same monitor new is the only comparison that decides anything. What holds instead is simple: the description of the self-test feature check as a way of checking whether the monitor is working properly as a stand-alone device, the list of screen abnormalities that call for the integrated self-test, which includes colour fade, the instruction that the steps live in each model’s user guide under Troubleshooting rather than in one key combination, the separate route for monitors with a joystick, the two readings of the result, and the Factory Reset option in the On-Screen Display menu, are read from Dell’s article 000124390; the gesture of the monitor check — unplugging the video cable, plugging the power cable back in and turning the monitor on — is read from Dell’s article 000126004; and the description of night light as a setting that shows warmer colours, the note that night light is not available with certain drivers such as DisplayLink or Basic Display, the note that a greyed-out night light toggle may mean the display driver needs updating, the statement that the Brightness slider may not appear on desktop PCs with an external monitor and that the buttons on the monitor are used instead, and the colour-profile operations of removing a profile and setting a default one, are quoted from Microsoft’s page on changing display brightness and colour in Windows.