I recently came across a new to me abbreviation in a post on a Green Party forum - "poc". ...." if our members don't vote a single poc candidate to the list's top three". Apparently it stands for person of colour and is subtly different from (to?) BME or BAME and means only the black

To me it sounds like the worst sort of mealy mouthed linguistic contortion and abuse of language. If you mean black, say black. If you mean people with a skin colour more than two standard deviations away from the mean skin colour of the UK population in the direction of a dark chocolaty brown [insert pantone reference here]  then say so - though why you would want to draw that line is beyond me. My family all used to be shades of grey until the mid sixties when we acquired a range of pale pinky yellow reddy colours according to the photographic record.

If you actually mean people at least two of whose grandparents were born in sub-saharan African or the West Indies then say so.

And as for having quotas for candidate selection then that is the worst sort of liberal sticking plaster covering up a deeper problem. We should be treating the underlying problem (not enough members and not 'enough' credible candidates coming forward reflecting the balance of skin tones or ethnicity in the communities they seek to represent), rather than the sympton [bad spelling] of the candidate list as selected.