The Choice of Color Space for Raw Conversion article in Guide to Mirrorless is a good test for whether your display is up to snuff in wide gamut and calibration (but it’s mainly an article about the Olympus EM1 behavior). For a general and similar discussion of gamut, see Wide Gamut Colorspace Reduces Noise, Avoids Posterization in DAP.
On my NEC PA302W (and even my 3-year-old LCD3090WQXI which is older than my NEC PA301W), the difference between sRGB and ProPhotoRGB is obvious and substantial. But even on high quality laptops such as the MacBook Pro with Retina display, the gamut is relatively narrow and the logo is invisible*.
If you can’t see it, you can’t edit it properly. Digital cameras have awesome gamuts these days, and printers now exceed AdobeRGB. Don’t whack your images in editing by literally blinding yourself to shades of color. Don’t get suckered into faux calibration, and don’t calibrate to a truncated gamut.
Recommended wide gamut displays (PA302W is first choice).
Can you see it?
There is a large “DIGLLOYD.com” on this blue road sign image (starting at bottom left corner). The image is in the ProPhotoRGB color space. To see it, the display must have the gamut to distinguish the shades of blue, proper calibration and profiling must be in place, and the web browser must respect color spaces (most do these days)**.
Ironically, the logo is visible on some iOS and other devices, because iOS displays color inaccurately (no support for color spaces)*.
This is a flawed demo (but nothing to be done): bad calibration or profiling or software non-suppot of any kind can also make it visible on any computer or device (e.g., choosing the wrong profile in the Displays preferences). Visibility is NOT a proof here of gamut; please see the original large images in the Choice of Color Space for Raw Conversion article in Guide to Mirrorless.
* It could be visible if using a web browser that does not support color spaces, but the image as a whole would also be wrong (inaccurate).
** Apple iOS devices ignore color spaces, so they are useless for displaying anything but sRGB, and iOS displays any other color space incorrectly (can look a little different only, or quite flat and dull, depending on colors).