For me, United''s home shirt should always be broad red and white stripes on front and back and on sleeves. Red stripe being the middle stripe. No ifs or buts. The shorts, not too fussy but I like to see Utd in black shorts for a home kit with white socks, but can live with white shorts and socks.
Away kit...for me should be predominately white cos we look smart as fuk with a white shirt on (Utd's first jersey was white) with red / black supplementing. For a third kit, I quite like a yellow shirt with a white or black shirts/socks. We wore yellow shirts away a lot in the 80s and some of em looked well smart. Trouble is we were crap away from the Lane most of the time.
Any blue/purple/orange abomination should be outlawed.