Thank you, I have to put that in the ex_config file with the assigned material. I think it will be like that, thank you, I'll try.Use this in "ext_config.ini"
[TYRES_FX]
GRASS_COLOR_A = 250, 250, 250, 0.06
GRASS_COLOR_B = 250, 250, 250, 0.06
;;; or this if its not a grass surface
; DIRT_COLOR_A = 250, 250, 250, 0.06
; DIRT_COLOR_B = 250, 250, 250, 0.06
SURFACE_TYPE_0 = see_this