Rigging - Why is my bone blue? I selected a bone and then tried to add another bone to the selection. But instead of the other bone getting selected, the first bone gets blue. I had to click another time on the second bone so I could actually select it.

What does the blue color indicate?

I made three clicks, I will post an image for each click, the red X indicates the bone where I clicked at.

First click



Now its blue... and the second bone is not selected



Last Click (why I had to click twice on that bone to select it?)
The second bone is a duplicate btw, there are two exact bones at the same place.
In Pose mode. the lighter blue color indicates the active bone, while the darker blue indicates a selected bone.