Blue Screen

How to use a blue screen

Each pixel of a typical LCD or OLED display is made of red, green, and blue subpixels. A pure blue field, #0000FF, turns the blue subpixels fully on and leaves the red and green ones off. That isolates one color channel, so a fault in it stands out.

1. 1

   Open it full screen. Browser toolbars around the field hide the edges and corners, where faults often sit.

2. 2

   Turn off color filters. Night mode and blue-light filters reduce blue on purpose, so the field can look dim or tinted with them on.

3. 3

   Clean the display first. A speck of dust can look like a dark pixel. If it wipes away, it was not a fault.

4. 4

   Look closely. Blue looks darker to the eye than red or green, so a missing blue subpixel is less obvious. Scan one section at a time, and move closer to anything that stands out.

What a blue screen can reveal

A dark dot is a pixel whose blue subpixel does not light.

A red, green, or other colored dot is a pixel with a subpixel stuck on, lighting a color that should be off. Against deep blue, a stuck green or red subpixel is usually easy to see.

Uneven color, such as patches that look lighter, darker, or more purple than the rest, can point to uneven backlighting or panel variation. A small amount is normal on many displays, so check the manufacturer's warranty terms before deciding a panel is faulty.

Check all three channels

A fault can affect one color channel and not the others. Together with the Red Screen and the Green Screen, the blue screen covers every subpixel of the panel. If you find a dot that stays put, confirm it with the Dead Pixel Test.

This screen's exact value has its own #0000FF color page, with its RGB and HSL values and its contrast against black and white.