Okay, thanks anyway for your astuce.
I don't think the LED effect required a lot of complex work from an expert in graphics and rendering under a sophisticated software, but just a simple way to disable the lightmodel on only one surface among others and without impact these surfaces.
The subject could have been titled quite simply:
"How to Disable the lightmodel of a Single Surface without Impacting the Others?"
I think, in the future, a simple line of codes in the Maple's display command could be look like this (or similarly):
L := LIST_OF_LIST_OF_PLOT3D_OPTIONS:
for i in L do
if member(lightmodel = none, L, i) then IGNORE_AMBIENT_PROCEDURE( ... )
else lightmodel = light3 # Default value
Maybe an amendment to update the display command in the next version coulb be submit.