Cyan Screen Test: Check Blue and Green Channels, Banding and Uniformity Online
Cyan is green and blue firing together at full strength while red stays dark — one of the two cold secondaries that pure red, green or blue fields never exercise as a pair. This free fullscreen cyan page floods every pixel with pure #00FFFF, so channel imbalance, banding and pixel defects stand out immediately.
What to look for on a fullscreen cyan field
Press F for fullscreen, sit back and sweep your eyes slowly across the screen — defects jump out in peripheral vision faster than under direct staring. On a healthy panel you should see one flat, even cyan from edge to edge. A red-tinted or dark dot that never changes is a dead or stuck subpixel: on cyan the red subpixel should be fully off, so any dot that glows, flickers or looks darker than its neighbors is a fault worth confirming on the dead pixel page.
The field itself carries the diagnostic weight. Any pinkish cast means the red channel is leaking — it should be at zero. And banding is unusually telling here: because cyan is built from exactly two channels, visible stripes almost always trace back to the blue or green side of the chain — a struggling cable, limited output range or weak driver electronics on one of those two channels. If the cyan also looks brighter in the center or washed out toward the corners, finish the inspection with the all-in-one screen test to compare against fields that light all three subpixels.
Practical uses and fixing what you find
A fullscreen cyan field is the cleanest way to test how a display handles paired cold channels, which matters more than it sounds: plenty of content lives in the cyan range — skies, water, teal UI accents, medical and scientific imaging. Because red is fully suppressed, the field also doubles as a red-suppression check: any red contamination you see is a white-balance or channel-leak problem, not your imagination. Photographers and print-shop operators use it for exactly that, since a display that tints cyan toward pink will betray every cool-toned image.
Fixes follow the diagnosis. A red leak across the whole screen is usually a picture-mode or color-temperature setting — reset to Standard/sRGB or recalibrate with the color calibration page. Banding in the stripes points at the blue or green path: swap in a better cable, set the GPU to full RGB range, and disable dynamic-contrast enhancers that quantize the signal. A confirmed dead or stuck subpixel is hardware — check the warranty rules on the dead pixel page, and give the stuck-pixel cycling pattern a few hours before accepting the defect. Then re-run this field: whatever changed should be visible within seconds.
Frequently Asked Questions
What is a cyan screen test?+
It fills the display with pure cyan (#00FFFF) — green and blue at maximum, red off — to check secondary color accuracy, channel leakage, banding and pixel defects on a color that primary-color fields cannot fully cover.
Why does banding on cyan point to the blue or green channel?+
Cyan is made of exactly two channels, so a stripe in the field means one of those two is being quantized or clipped as levels step. If the stripes were a general processing or cable problem they would appear on other fields too — on cyan they almost always trace to the blue or green path.
What does it mean if cyan looks pink or purple?+
The red channel should be fully off on pure cyan, so any pink or violet cast is red contamination — typically a wrong color-temperature preset or white-balance drift. Reset the picture mode or recalibrate; if the tint varies across the screen, the panel itself is biased.
Is a cyan screen useful for anything besides testing?+
Yes — its high brightness with no red component makes it a calm, cool-toned backdrop for checking red leakage, and a distinctive signal color for kiosks or status displays where you need maximum visibility without a warm alarm tone.