@duerer
In Blender, the RGB and HSV/HSL values are in Scene Linear color space
This is not correct imho; this is obviously not linear:
Same with RGB (0.5, 0.5, 0.5). And like @blanchsb mentioned, with Texture Paint Brushes, RGB and HSV are linear.
The Hex values are always linear (see my beautiful image above), and if they are Gamma corrected, then with a Gamma = 1.