How to change the number of channels in a file?

[Caitlyn21844307y7g8]

I recently posted about an issue I was having with colors looking different from file to file, even though they appeared to be in the same color space. Never had a satisfying resolution to that problem, but I recently discovered via that panel that the reason for the discrepancy was that one of my files has 3 channels and the other has 4. 

I admittedly know nothing about channels, so I have no idea what this means or how to fix it, but I'm somewhat certain that this is the issue since it's the only noticeable difference between the two files. I also tried plopping another 3 channel file into this 3 channel file and the colors showed up the same, unlike when I place the 4 channel file in there.

If anyone has any advice on how to solve this problem I'd be eternally grateful as this has been plaguing me for months.

[c.pfaffenbichler]

Could you please post screenshots with the pertinent Panels (Toolbar, Layers, Channels, Options Bar, …) visible? 

[D Fosse]

Probably an alpha channel. A screenshot of the panel will confirm as c.p. says.

Alpha channels have no effect on how the file looks.

It's much more likely that you haven't embedded the color profile in some files. Always make sure the profile is embedded.