They're shaders, you're more than likely talking about a calling card shader.
I can't put it the easiest way to understand but you need to precache the shader, inside init put:
PrecacheShader("ShaderNameHere");
You can find a shader here:
You must login or register to view this content. & put a desired shader where i said to.
Then you'll have to call it somewhere throughout your script, most menus have storehuds, which is called when the menu is open to show the HUD's, thats where you'd call it, although then you have to add to open / close functions to hide the hud when its closed and show when its opened, etc.
Easy, but if you don't understand maybe you're better off grabbing a menu base with this included already.