Re: Can't find colored jos, so...........
Hm, when using a jo I don't look at it. Neither when doing aikijo nor when doin jo jutsu.
So I wouldn't see or recognize colours on it while using it.
Second: In most dojo I know, the only colours - black and white left aside - can be found if shomen is decorated with flowers.
A coloured jo would be very "disturbing".
(I think most dojo I know, would offer the owner of a coloured jo one of the dojo-weapons. Very politely, but firmly.)
Third in our training we "exchange" the ends of the jo. There are a lot of such changes. They seem typical because a jo is not a yari or naginata or bo.
At last: My own weapons have been expensive and are handmade. I would regret it if the colour of someones jo would rub off on them.
(I've never seen a coloured jo in all those years. Isn't this more playing then practicing?)