NS locomotive queestion

First posted this on the Trains locomotive board with no response so thought I would try here Does anyone know why some engines are painted white around the cab number boards?

I think it has to do with the paint scheme. The normal older paint scheme doesnt have the white “unibrow” with the numberboards. The newer locomotives or the freshly painted ones use the newer paint scheme with the white “unibrow” by the number boards. Hope that helped!