According to this link:
https://www.reddit.com/r/roblox/comments/4aroyd/clonetrooper_found_a_hack_that_allows_meshes_to/
SpecialMeshes can be made neon through textureid I think. But the link in the post leads to a 404. I can't seem to find a solution, so this is the only solution I could think of.
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I found this http://wiki.roblox.com/index.php?title=File:GlowingMeshColors.gif
^ yeah but you can't see the NeonProxy in the gif which is pretty much the entire point
SpecialMeshes cannot be made neon through textureId, using the meshid and textureid in the gif kingdom posted does not result in a neon part https://i.gyazo.com/d37c824acd4355bb48770be572cba888.mp4 (right is actual neon, left is using the texture/mesh from gif
basically what the reddit post says is that clonetrooper found a really hacky way that worked but the tutorial didn't get migrated to the new wiki (yet?)