SurfaceGui method
Step 1 : Insert a part then stretch it
Step 2 : Insert a SurfaceGui into the part then insert a frame into SurfaceGui
Step 3 : Select SurfaceGui then set LightInfluence to 0
Step 4 : Select the Frame then set the Size to this [1,0,1,0]
Step 5 : Change the BackgroundColor of the Frame to Green or Blue
Result
Neon Method
Step 1 : Insert a part then stretch it
Step 2 : Set the material to neon
Step 3 : Set the color to green or blue and lower the value to the
point where you can’t see the bloom effect
Result