The color refers to the frequency of infarction at each voxel. The highest frequency of infarct occurrence is in the centrum semiovale and striatocapsular and insular regions.
Phan, T. G. et al. “A Digital Map Of Middle Cerebral Artery Infarcts Associated With Middle Cerebral Artery Trunk And Branch Occlusion”. Stroke 36.5 (2005): 986-991.