Try lowering the Brightness/Range of the SpotLight settings.
If the decal is neon material, if you add a transparency to it, it can lower the neon effect on it. If you don’t want it too transparent, you could always create a SmoothPlastic white piece behind it too.
The thing is, the decal is not neon material, I’m pretty sure it looks like it’s neon because of the brightness of the spotlight on the decal. I was wondering if there was an alternative to achieve the same lighting but without it making the decal appear neon.
Add “Bloom” to lightning and decrease the amount of it. This should fix the problem.
Try increasing threshold, decreasing size and decreasing intensity.