When I first heard the term "person of colour", I thought it was a joke to take the piss out of political correctness, much like "person of size".
We are all "of colour", and a true non-racist (or simply, a Physicist!) will understand that.
With that said, some of those posters are just whining (#1 is not racist, just uneducated), others are pretty funny (#47 - more Pakistani English speakers exist than British), one in particular is a baseless accusation of "institutional racism" in one of the most racially-free countries on Earth (#27) and a *few* seem genuine (e.g. #40 - although I would say that the colour of your skin should have as close as possible to zero influence over your identity).