Hi Matt,
Thanks for getting back to me.
I can confirm that changing the image profile to "sRGB" seems to fix it.
Re my display profile / system:
I'm using a Macbook Pro 15" (2014) and OSX Yosemite (10.10.5 currently but the issue occurred on previous versions also).
My current display profile (just using the built-in LCD) is "Color LCD" but the issue occurs whether i'm using the built in display or a monitor connected via HDMI.
As far as the color wheel is concerned, it looks correct before i open the screenshots:
but not after i open the screenshot:
Once i "assign" the sRBG profile to the document, it goes back to normal.
Out of interest, i changed Designer's active profile to "Display" and tried opening the screenshots again but it didn't seem to help. I would have thought there should be no transform when the active profile is the same as the image profile?
Cheers,
Chris