The Tuesday Birthday Problem

I have two children. One is a boy born on a Tuesday. What is the probability I have two boys?
The first thing you think is “What has Tuesday got to do with it?” Well, it has everything to do with it.
Answer:
Red means “outside the reference class”. Yellow means “in the reference class but not boy-boy”. Green means “inside the reference class and boy-boy”.
Boy-boy in the reference class occurs with probability Green / (Green + Yellow) or 13 /27