Black and white
Sometimes it takes the realization of an illness, or the vast expense of time to find the respect of seniors and juniors being equal in Seiza.
Many times, both in class, and in seminars, the senior black belt, who are instructors or teachers, will invite juniors to fill in the front line ... not because they are juniors, but to understand the equality we all share when we give our respect and appreciation for what we learn in Aikido classes and sometime into our private lives.
The way I was taught to look at the journey to higher ranks in martial arts was that when you finally attain the highest rank, 10th dan, you have completed the circle to white belt to begin the journey again ... white belt. With this ideal, your personality will always be humble, caring, and respectfull of all things, and all beings, even though your knowledge is immense.
I have seen, and been a part of the colored belt system, but in many cases the students mistook it for seniority and not a case of bookmarking the knowledge given to the student. Colored belts should be no more than the accomlished practice of knowledge given, no more and no less. It should not be a status symbol, or banner to waived in an overlording manner.
So, if asked how important the colored belts are, Black and white is all we should need.
If asked how effective is Aikido training your answer should be found in your practice, not in the colored belt, or the seniority of lining up for practice ... unless we are becoming a neo-military unit?
By the way, did you ever notice how many Sensei who visit, or attend seminars line up in the back rows for practice?
It doesn't seem to make a difference to people who are comfortable with themselves and Aikido practice.