You do several things wrong here, but I suffered from same problems back when I started, there's nothing to worry about.
Lua doesn't actually know what Smooth Plastic, or Neon is.
Instead it knows what Enum.Material.Neon or Enum.Material.SmoothPlastic is, because this time it doesn't treat those as ordinary string, but as types which can be assigned to different things.
You can find literally everything in Enum.
Enum is translating things that only we humans know, to lua.
Also Note to make sure that your script is server script and not Local Script
4 comments
wait should be in the end
tho this script does not make any sense
math.random(1, 2) and use enums (Enum.Material.MATERIAL_NAME)
how does this not make any sense? while true do (infinite loop) then change material, wait a random number, change material