[Quoth]

I agree, none are actually white.
Also most paper gets brighter white even with blue or UV source.
Interestingly the eInk screens are very dark in a room with UV LED insect death, pulp paperback is dark, but POD sourced books, paper for printer and magazine white are bright

Most CFLs and fluorescent tube lamps have a peak greenish hue and will make eink look greenish/grey compared to printer/copier paper which will mysteriously still be white. So don't use copier/printer paper to set electronic camera white balance.

Also the camera -> processing -> local screen will not match what the human sees. None of my desktop screens and laps have the same colour temperature or rendition. The 23.5″ LG 4K UHD HDR is the most natural and least blue tinged (cheaper tablets and laptops use poor colour temp and rendition phosphor doped blue/violet LEDs. Native white LEDs don't exist. It's why LED lamps when off look yellow and glow yellow under UV).