I don't ever remember a time when it was OK to ignore skin colour - it's what a person is.  The 1958 comedy No Time For Sergeants poked gentle fun at the southern hillbilly character played by Andy Griffiths who is innocently shocked to see a black lieutenant and is told colour doesn't matter.  He then takes that principle as far as claiming not to notice that another officer is actually a woman. Much laughter ensues.

And by the way, that was at a time when the southern US still had separate water fountains for 'whites' and 'coloured.'