Tiny change and very nice too It's boring and almost impossible to compare all color schemes just by click.
Not exactly what you asked for, but have you tried the Schemr plugin?
It allows you to quickly change colour scheme via the command palette.
I second a request for this feature. I get the impression that image is important for sublime text; a mouse hover colour scheme change allows quick and easy aesthetic alterations, which I believe goes hand-in-hand with the way sublime text presents itself as prettier and more useful than competing text editors.