Operating system and graphics card
Fedora Linux 29
Broken: 2.80alpha 2 2018-11-22
Short description of error
When entering color as a hex entry, Blender reinterprets it and shows a different value, because the computer knows color management way better than the banana loving ape in front of the screen.
Exact steps for others to reproduce the error
Go into, say, world color, switch to hex color view, enter ffffff, but blender insists on showing ddcfd8 (with a note that it's gamma corrected). I would expect all the color management to happen on top of the input value rather than adjusting the input value.
Here's a show screencast of the situation: http://jimmac.musichall.cz/stuff/unexpected-hex-entry.webm