Please excuse me for the newbee questions, but I´ve noticed that similar (at least I think so) rankings, have different colour belts associated with them. I don´t know if it depends on the country or just the dojo, but it confused me a little bit.
I´m in Brasil righ now, where I´m facing White/Yellow/Purple/Green/Blue/Brown, but I´ll probably be heading back to europe where they have Orange and Red somewhere in the middle.
So how does it actually work?
After some reading, I´ve came up with a note refering that there were even some dojos that only recognise White/Black.
Are the sistems recognized between each other under the same "branch", or am I missing something?
Every style does it slightly differently. First off, yes, I have heard of some schools that only do white/black rankings, and giving my test anxiety, I almost wish I was in one.
The colors are also different based on style, and possibly countries in the same style, I'm not sure of that, but if there are rankings, they are the same number wise. It's the number that will remain consistent. The number system as far as ranking goes is always the same, kyu ranks count down, so 10th kyu is the lowest, and 1st kyu being the closest to shodan, and dan ranks always go up, so 1st dan is the lowest dan rank. Although some schools don't start at 10th, if you have an ikkyu and a sankyu, the ikkyu will always rank the sankyu, regardless of the color of the belt.
As far as other schools are concerned, it is my opinion that if you are going to attend class at a dojo not affiliated with the one where you received your rank, you should wear a white belt. The dojo cho will most likely ask you questions about your martial arts background, as well as Aikido, and at that point the dojo cho may tell you to wear your rank, or may not. I have taken classes for a few months in a different dojo that is physically close to me, and my first class I wore my white belt. The dojo cho then told me after that class to wear my belt of rank, even though the color doesn't even line up with their kyu rankings. However he did tell me not to wear the hakama, since in their style, only yudansha wear hakama, whereas in Wadokai, the women wear hakama at yonkyu and up, and men only at shodan and up.
I personally think it is an issue of respect to the dojo cho. Any class or seminar that I attend outside of Wadokai, I will wear my white belt, unless I am specifically asked to wear my belt of rank. But I also visit as many other Wadokai dojos as I can when I visit other cities, and I do wear my belt and hakama without question in all of our dojos.
Hopefully this helped!