How to fix "The document does not have an embedded RBG profile!?

[HeyoThere]

Recently I changed PCs and I started getting this message when I open my files. I realized that it was changing the color of my work and I can't have that, so I noticed that choosing the option "Leave it as it is (don't color manage)" does the trick but I want to know if there's a way I can make this warning stop appearing like on my other PC

[D Fosse]

You don't want that warning to stop. You want to do as it suggests  - assign a profile.

The color change you see is precisely because there is no embedded profile! If there was, it would be consistent everywhere. That's the whole point.

The image should always have an embedded profile. That's what defines the colors. Without a profile, colors are undefined and random.

Your color management policies should be set to "preserve embedded profiles".

[HeyoThere]

Problem is, when I do assign a profile it changes the color of my previous works, basically I wanna know how do I assign a profile that doesn't change the color I was getting on my older PC. I tried checking on my old PC's photoshop the embedded color that photoshop used, and tried setting the same one on the new PC Photoshop, but the message still appears.

[TheDigitalDog]

Problem is, when I do assign a profile it changes the color of my previous works, basically I wanna know how do I assign a profile that doesn't change the color I was getting on my older PC. I tried checking on my old PC's photoshop the embedded color that photoshop used, and tried setting the same one on the new PC Photoshop, but the message still appears.

By @HeyoThere

The color changes because the numbers now have a scale to describe them.

You need to assign the correct profile (which is a guess since it's untagged). Or try different profiles until you get the best possible color appearance from the new tag. It might be a display profile that is rather unique, or it might be a standardized RGB Working Space (like sRGB). But you have to figure out which and tag the image because without it, it's mystery meat RGB. 

[Stephen_A_Marsh]

Can you post screenshots from the original and new PC's Colour Settings?

[NB, colourmanagement net]

You are going to need to assign a profile. Bit not ANY profile -

That profile you assign needs to be the correct one [the colourspace that was used when the file was originated or last colour corrected] it's not the assign profile process that’s making your images look wrong per-se, it’s the assigning of an incorrect profile.

The moral of this story to bear in mind for the future - is to never save files without an embedded profile. 

I hope this helps
neil barstow, colourmanagement net - adobe forum volunteer - co-author: 'getting colour right'
google me "neil barstow colourmanagement" for lots of free articles on colour management