When I was picking my Pokemon Go team colour, I picked Blue because there were hardly any blue gyms, so I thought it would be good to go against the masses. Also because I liked the blurb of the blue team most.
Now I’ve realised that this was a really bad move, since it’s impossible to train up or hold any gym you capture on your own.
So I was reading up on whether it’s possible to change your Pokemon Go team colour. Unfortunately, it seems that at present there is no option to change your Pokemon Go team colour. The only option is to delete your account and start a new one.