1.Open by spark vehicles.img
2.Click one on np. ambulance.wtd
4.Find file with plate and click edit
(Usually are 2 files with plates. One nomal and one non colored. 
The non colore file replace with the same plate in non colored version or but empy file 
with is in bonus cause only few plates got non colored verison for better look 
but in game is almost no different.)
5.Replaced by my skin
6.Click save and exit
7.Click save and rebuild vehicles.img
8.Close spark. 
Finish!