Blue Screen
A full blue screen completes the set of primary-colour tests. Because a dead blue subpixel can stay hidden on white and grey backgrounds, showing pure #0000FF is the only reliable way to catch one.
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What this colour is good for
- Finding dead or stuck blue subpixels that white, grey and red tests miss.
- A saturated blue reference for video, web and print colour matching.
- Testing how uniform your panel looks in a low-luminance channel.
Blue is the dimmest of the primaries on most panels, which makes it the most forgiving and the least useful for judging brightness uniformity. Judge that on white.
Frequently asked questions
Why is the blue screen so dark?
Blue has the lowest luminance of the three primaries on an RGB panel, so #0000FF looks dim compared with #00FF00. That is expected, not a fault.
What is a subpixel test actually checking?
Each pixel is made of red, green and blue subpixels. A full-channel colour lights one subpixel per pixel. Any black dot on an otherwise even field is a dead or stuck subpixel.