I’m curious about the capping on this frame of brood - dark in the centre and lighter in the outer arc. And why are there two separate patches of brood. What do you think this means ??
The darker color is because the brood is in comb that has been used for brood more frequently than the area with lighter color cappings. The dark color comes from the buildup of leftover cocoons. The color makes it’s way into the cappings. You get the same thing when you put fresh foundation next to a black frame. You get a slight color transfer from the black frame to the new wax on the foundation.
I believe that the reason for the two separate patches of sealed brood is a result of the colony coming out of winter. During winter the colony constricts the brood & surrounds it with honey. As soon as the conditions are favorable in spring, the bees will open the brood up by emptying the honey out of the surrounding cells & placing it somewhere else or consuming it. This allows the queen to lay in those surrounding empty clean cells. That would explain the two different stages of brood & the lighter color.
On the top left of the photo might be a second stage where the cells have been emptied in readiness for the queen to lay in.