Excerpt from Adobe Lightroom 2 – The Missing FAQ
Usually a mismatch in colors is due to either incorrect color profile settings or a corrupted monitor profile.
For example, a ProPhoto RGB photo mistakenly rendered as sRGB will display as desaturated and flat.
This is a ProPhoto RGB photo correctly displayed as ProPhoto RGB:
This is a ProPhoto RGB photo incorrectly displayed as if sRGB:
First, check your color settings.
In Photoshop, go to Edit menu > Color Settings to view this dialog.
The RGB Working Space is your choice, but whichever you choose to use, you are best to set the same in Lightroom’s External Editor preferences and Export dialog. We’ll come to that in a moment. [Which color space to use is a subject for another post!]
Selecting ‘Preserve Embedded Profiles’ and/or checking the ‘Ask When Opening’ for Profile Mismatches in that same dialog will help prevent any profile mismatches.
‘Preserve Embedded Profiles’ tells Photoshop to use the profile embedded in the file regardless of whether it matches your usual working space. ‘Ask When Opening’ for Profile Mismatches shows you a warning dialog when the embedded profile doesn’t match your usual working space, and asks you what to do.
You also need to set your External Editor settings in the Lightroom Preferences dialog. It is simplest to use the same color space as you have chosen in Photoshop.
You’ll also want to check the color space that you’re using in the Export dialog, and again, choose the same color space for photos you are going to open in Photoshop.
As long as your Photoshop and Lightroom color settings match, or you have Photoshop set to use the embedded profile, your photos should match between both programs.
Other mismatches when the color settings match correctly can also be due to a corrupted monitor profile, which you’ll remember from a previous post.