If you see that smokey, green or grey color in your lawn it is a good sign that the grass is not getting water in those spots. Check for blocked or broken sprinklers in that location.
Grey color in lawns is usually from wilting and it is the first stage before it turns brown. Catch it early and run an irrigation cycle to relieve the drought stress then discover the cause.
In the top picture this has been a problem for awhile because the spot has already started to turn brown and grass started to die due to drought. Either the spray head is blocked or plugged most likely.