Sorry, I should have been more clear. What I was referring to above as a "colour profile" is an ICC colour profile. See this page for more information on ICC profiles.

I have colour management turned off in Photoshop, however Photoshop's "save for web" still gives me the option to insert an ICC profile when saving as a JPG, but when saving in PNG format, it inserts the ICC colour profile without asking and there is no option to turn it off. This is why I think that it's something for people to consider as other programs may be doing the same or similar things.