Moth3r said:

In theory, it would be a new skin selectable in the user preferences.

However, certain people have been asking Jay to put the light blue skin back for years...

A user selectable skin would be great, especially if there was a sticky to say 'if you want to see correct colour in images on this site, select this skin'

When using this site now for more than a few minutes, your brain decides that the blue background is actually grey and shifts your colour perception accordingly.