Re: Colored Belt or White,
Our club uses three colours for our kyu grades (white = 6th, yellow for 5th and 4th, brown for up to 1st). The club is somehow affiliated with Aikikai, ie. our yudansha grades are Aikikai grades as recommended by the head of the club's association.
My sensei explained to me long ago that one reason was a safety thing. As there are a bunch of dojos in our club in which w,e at times, do visits in between our dojos. A quick identifier to a partner who you haven't trained with or seen for a while is; don't toss around the white ones (newbies), the yellow ones are still learning ukemi (only a couple of years experience), the brown ones should be able to receive the techniques (more than a couple of years taking fall).
Otherwise, whenever I have travelled to a seminar or trained at a non-affiliated dojo, I carry/put on the white belt and humbly request to the senior student if I should wear my black one and hakama.