The two above photos show randomly shaped green (non-dormant) patches of bermudagrass rough. These patches were a result of leaves piled for removal left overnight when we had a hard frost. The leaf pile insulated the turf from the cold air, and helped retain some of the warm air in the soil. The result was these areas did not develop frost and thus did not enter dormancy.
The photo above shows the effect of using green divot mix on a practice tee. This tee is not overseeded, but the green, non-dormant patches of bermudagrass are a result of warmer soil temperatures created by the green sand being warmed by the sun. Several clubs with ultradwarf bermudagrass greens utilize black-dyed sand on their greens to promote warmer soil temperatures. The goal is to extend the growing season of their greens, and to reduce how long the soil may remain frozen.