Light style: Background grey tones are inconsistant with GNOME application UI
Image to visualize the problem:
GNOME Shell is using colours from the GNOME Palette - e.g. "Light 2" and "Light 3" - for backgrounds of panels and popups. These palette colours have a slight warm tone. This does not match either Gtk 3 Adwaita applications - which use an even warmer tone - or Gtk 4 libadwaita applications - which use pure white as a base colour, and shade it with pure black to produce completely neutral/unsaturated greys.
For consistency with modern GNOME applications, the shell should use a neutral grey tone. It might make sense to look at some libadwaita applications and choose a shade of grey that matches one of the shades used there.
Another example of where this issue is visible is window menus:
The warm tone of the palette grey doesn't match the neutral tone of the libadwaita window.