Purple screen

A full screen of purple at sRGB 128, 0, 128, driving red and blue at half intensity with green fully off.

Dim 100%

Download as PNG

What this test can and cannot tell you

This page sends your display an exact value (#800080, or 128, 0, 128 in RGB) and fills the screen with it. That part is reliable.

What comes out the other side is not something a browser can see. Your panel, your operating system colour profile, your brightness setting and the light in your room all change what you perceive, and nothing on this page can read any of them. Judging colour properly needs a colorimeter; judging a fault needs your eyes on a clean field, which is what this gives you.

The dim slider is the one control that changes what is sent to the panel. Leave it at 100 per cent whenever you are making a judgement about the display.

More on this: what a browser cannot detect and how these measurements work.

What a purple screen is for

Switching green off entirely

Green is fully off on this field while red and blue are both working, which makes purple the counterpart to yellow: it is where a green element stuck in the on position gives itself away. Such a pixel appears as a small greenish or unusually pale dot against the purple. Since green carries most of the perceived brightness in sRGB, a stuck green element is one of the more distracting faults to live with, and this is the field that isolates it.

A half-intensity field, and why that matters

Purple as defined in CSS and in the classic web colour list is not full red plus full blue. It is both at half, which makes it a mid-tone rather than a saturated corner of the colour space. That is useful, because mid-tones are where banding and dithering artefacts live, and a flat purple field will show stepping that a fully saturated field hides. If you want the fully saturated version, drive red and blue to maximum on the full screen colour test for magenta instead.

Spotting compression and dithering artefacts

Purple and magenta tones are historically difficult for video compression, because they sit at the edge of what chroma subsampling represents well. On a streaming device, a long cable run or a capture card, a flat purple field is a good place to look for blocking, banding and noise that never appear on neutral content. On a display running in a limited colour mode, the same field often shows visible steps where it should be smooth.

Checking a wide-gamut display in sRGB mode

Purple is one of the tones where a wide-gamut panel running without colour management looks most obviously wrong, tending to render more vivid and more blue than intended. If this field looks electric rather than muted, your display is probably stretching sRGB content across a wider gamut, which affects every colour you see and is worth correcting in your display settings.

How to run this test

Go full screen and let the field settle.
Look for greenish or unusually pale dots, which are green elements stuck on.
Check the field for visible steps or banding, since this is a mid-tone rather than a saturated corner.
If the purple looks electric rather than muted, check whether your display is stretching sRGB across a wider gamut.

What a problem looks like

Greenish or pale dots: A green element stuck on. Because green is the brightest primary, a stuck green element tends to be the most noticeable of the three in everyday use.
Visible steps in a flat field: Banding across what should be a single uniform tone points at limited bit depth in the signal chain or an aggressive display setting rather than a panel defect.

What to do next

If something looks wrong, check it again in a normally lit room and from straight on, then check whether it appears on a second device. If it only happens on this screen and you are still inside the return window, that is the time to contact the retailer.

Questions people actually ask

Is purple the same as magenta?

No. Magenta is full red plus full blue, sRGB 255, 0, 255. Purple as used here is sRGB 128, 0, 128, which is both channels at half intensity. Magenta is the more saturated field; purple is the better mid-tone test.

What fault does a purple screen reveal?

Green is fully off, so a green sub-pixel stuck in the on position shows up as a greenish or pale dot. That is difficult to spot on white, where green is meant to be lit, and on green, where it blends into the field.

Why does purple look different on my phone and my monitor?

Phones frequently use wide-gamut OLED panels with saturated presets, while many monitors sit closer to sRGB. Without colour management the same purple values are stretched further on the wide-gamut screen, so it looks more vivid. Neither device is broken.