For the people who don't believe this, here's a Python program:

    x = [(c1,c2,d1,d2)
            for c1 in ["B","G"]
            for c2 in ["B","G"]
            for d1 in [0,1,2,3,4,5,6]
            for d2 in [0,1,2,3,4,5,6]
            if (c1 == "B" and d1 == 1) or (c2 == "B" and d2 == 1)]

    num = sum(1 for (c1,c2,d1,d2) in x if c1 == "B" and c2 == "B")
    denom = sum(1 for _ in x)

    print("%s/%s" % (num,denom))