I trained at a CTC for five years, until recently. The white and blue belt is the Combatives belt, which you receive for passing your Combatives test. You have to do six months to a year (instructor's discrection, I believe) of Master Cycle classes and sparring to receive your full blue belt.
As for whether or not it is worth it, it definitely won't help you beat other BJJ practitioners in a roll or tournament setting, but isn't really meant for that. It will give you a good sense of what it's like to use BJJ against strikes, as well as a solid (albeit small) foundation of knowledge to build upon. Some of the techniques are useful in all situations, such as the Elbow Escape and Double Underhook guard pass, while others are specific to situations where your opponent is intent on striking you.
I liked Combatives, and even after I had earned my blue and purple belts I still continued to attend every Combatives class.