As it is (as far as I know), areas of blocked line of sight are always black. I we would like to be able to color code this. Black is good for representing lack of light, but not other conditions. For example, a forest could be green instead of black. Smoke/fog could be white. Etc. With options like UDLPasswall players don't instinctively know if their line of sight is blocked by lack of light or a wall. Maybe the color of the over "darkness" could be based on the color of the next immediate dynamic light layer lines in that direction? So if a forest is to the left of the token they see green, but the wall to the right shows gray.
