Convert to Profile is quite different. Not only does it assign a color profile to
the document, but it tries to keep your image looking the same on screen.
It does this by processing the color data contained in the file for each pixel.
Converting to a new profile will more likely preserve a document’s color on
screen, but the data contained in the file will be permanently altered. Use
with caution.
If you’re copying layers from one Photoshop document to another, you will
want to ensure that the documents have been assigned the same color
profile.
Illustrator is the Same as Photoshop
If you would like images saved in Illustrator or imported from Illustrator to
Photoshop to match as well, then follow the steps below. These instructions
are for Illustrator CS5 on Mac and Windows. Setting up Illustrator CS4 is
very similar.
Step 1: Go to Edit → Color Settings, and set the working space for RGB to
Monitor RGB.
Step 2: Open the document and go to Edit → Assign Profile. Then set it to
Working RGB. This must be done for every single document you work on.
Step 3: Ensure that View → Proof Colors is turned off.
Step 4: When saving files with Save for Web & Devices, ensure that Convert
to sRGB is turned off. If you’re saving a JPEG file, then also turn off Embed
Color Profile (again, you may want this turned on for certain photos, but
chances are you’ll want it off for interface elements and icons).