As you work with images, you are going to move the images between the devices. When you move your images between different devices, bear in mind that different devices (scanner, monitor, printer etc) have different gamut (range of colour). Each device works within a specific range of colour variations that it can display. Because of these variations, colours may shift in appearance when you move images between different devices.
The problem of working with different colour spaces can be solved by using a colour management system. Colour Management system in Photoshop handles these choices and they can be set up in Color Settings dialog box that’s found under Edit menu (Edit->Color Settings).
Here’s a screenshot:
The settings you choose in Color Settings dialog box will define how the colours are being applied for RGB and CMYK.
Here’s a screenshot of Color Settings dialog box:
So what’s happening when you open a file in Photoshop? Well, Photoshop is comparing colours in your file’s colour space with the colours defined in Color Settings dialog box. What I do when I set up colour in Photoshop is I check option called: Ask When Opening. If this option is checked, Photoshop will ask you what you want to do if the colour spaces don’t match.
I hope you find this information valuable. Enjoy! 🙂