@tec - I agree it is a matter of judgement but the actual colour of the t shirt is a fact, no? :) - assuming we both see the same thing of course.
@ Gopher - clearly you're right about the colour chart. Without it we don't have enough information to resolve it at present. Even with a colour chart - which one do we choose? Aren't we simply using someone else's definition of maroon, unless of course we accept the definition of the wavelength of light corresponding to maroon as you suggest and hire a lab to test the t shirt. If I went to that length to make my point I think I'd be sectioned lol. Up to that point, what is a fact seems to me to be somewhat moot. But there is a fact lurking in there, presumably somewhere maroon has a definition that isn't subective. I don't want to stretch the illustration beyond what it can support though :)
I like your observation regarding something not subject to debate or opinion. There are lots of things that definitely qualify as facts, I agree. There are probably lots of things that are facts that we don't have enough information, at the moment, to state are categorically facts but that are highly likely to be facts. There are probably things that that we consider to be facts, but aren't. There certainly have been in the past.
I suspect a hundred years ago the classical view of atomic structure in physics was considered an unassailable fact. It wasn't though :)
@apog - you believe the theory of relatively is a fact, the theory is of course - it definitely exists, but I get the point you're making, you mean that in practice it is a fact? Interestingly even Einstein was convinced it wasn't a fact and said he expected to be proved wrong in parts at least. The layman, including me, definitely can't form a judgement as to it's factuality (is that a word?), we have to trust others. If next week Physicists come up with a variation to it I'd be none the wiser (though better informed :))
The shape of the planet though is something we can form a view on as there is a lot of evidence we can examine for ourselves, if we have enough money and don't mind heights we can even go into space and see the fact for ourselves.