What color profile is being used in PhotoShop when Proof Colors is OFF ?
I always thought it's system color profile but it turns out it looks very different when I enable Proof Colors to "Monitor RGB".
PS. I'm using PS 6 and Windows 7.
The color profile used by Photoshop when Proof Colors is off is the one set on the Edit > Color Settings screen in the 'Working Spaces' section. The exact profile used out of the 4 listed in that section is dependent on the format of the image being viewed, with 'RGB' used for color images and 'Gray' used for black and white images. The 'CMYK' and 'Spot' settings are unlikely to be used in photography.