I've been thinking recently that i'd like United to have an identity - yeah we have our red and white shirts, but so do many others. We often change the colour of our socks from Red to White to Black. The best kits for me are Black shorts and White socks, but we continue to mix it up.
There was the Morocco v France game in the World Cup where both teams wore tri-colour kits:
Man Utd 1st choice colours are Red, White and Black, it's their identity:
Hamburg too have their identity in tri-colour kits - White, Red and Blue (with the socks always featuring the chequers on top):
So, i'd like United to go as follows:
HOME - Black Shorts, White Socks
AWAY - White Shirt, Black Shorts, Red Socks
THIRD - Free reign, mix it up - but the 1st two kits should always be like that

That would then give us potential to mix up combinations if required - have shorts and socks available in all colours that match the kits. So if we're at Derby or Leeds for example, we just put red or black socks on:

If we're at Sunderland (red socks), we put black or white socks on:

Back to basics please Blades!