Annual Solar Exposure (ASE) refers to the percentage of space that receives too much direct sunlight (1000 Lux or more for at least 250 occupied hours per year), which can cause glare or increased cooling loads. Green is passing and other colors represent how much that grid point is failing. This can help with determining if a particular shading strategy is close or far from passing. See below for the legend.
More on ASE in cove.tool here.