Every once in a while a discussion/arguement breaks out as to whether you can learn Brazilian jiu-jitsu from a blue belt instructor. My short answer to this question is “absolutely!”
The long answer is “absolutely, but it really depends on the blue belt”. If the blue belt in question has a good overall understanding of the positions, strategies and techniques of Brazilian jiu-jitsu, and if he also has an ability to convey this information, then you can learn a lot from him. This is especially true when you are starting out in grappling: you need to build your foundation, and sometimes blue belts are very good at doing this because they were doing the very same thing not too long ago.
People will often argue that a black belt can beat a blue belt in sparring, so why shouldn’t you train with a black belt? It boils down to this: not all good fighters make good teachers, and I’d rather be taught by a good teacher than a good fighter. Would you rather learn to box from Mike Tyson or Angelo Dundee? In the best possible world you’d study with someone who is both a great fighter AND a great teacher, but this is a rare combination indeed.
On a personal note, my first Brazilian jiu-jitsu instructor was ‘only’ a blue belt and I learned a tremendous amount from him. In 1997 I started training with Pshemek Drabczynski (who was a blue belt under Carlson Gracie at the time), and I still remember and use many of the things he taught me: he gave me a great base to continue learning more advanced jiu-jitsu. Additionally I continue to learn from blue belts even today, because nearly every blue belt has at least one thing that he is very good at. If I ask the right questions, and watch that blue belt carefully, I can usually come away with one more piece of the grappling puzzle.