Am I correct in concluding Firefox is the only truly color managed browser?
I'm not sure any of the browsers are truly color managed. In theory Safari should be the best, but even Apple seems to have let their color expertise wither. Firefox may be the best of the rest, but it's pretty shaky too. Some programmers working on Firefox has a rush of blood to the head and (for spurious reasons) decided that they "needed" to write their own CMM, tossing out one of the best open source ones (LittleCMS). Needless to say, they didn't do a very good job, and now seem to have move on, leaving it to rot. It doesn't seem to handle cLUT based profiles either.