Why is different color with same guibg when on different platform?

[anhnmncb]

I use

:hi Normal guibg=LightYellow

to set my background, I find it has different looking when on windows
and linux. On linux, the color is right, but when on windows,
LightYellow would become darker, why?

--
Regards,

anhnmncb
gpg key: 44A31344

[anhnmncb]

Hmm, after I set the color code (#FFFFE0) directly, then the problem is
gone, I guess the definition is different on platforms.