How to illuminate the edges of an object in the bge First of all, I don't know if this is what I should call that effect. I'd like to illuminate an object's edges once the object is detected by a ray sensor in the game engine. For example, I'd like the edges to turn red when the ray sensor hits an enemy. Ive been looking up tutorials, but I haven't found anything. Please help.
There is no build-in option that provides you an outline effect.

But there are other options. E.g. via GLSL shaders.

Additionally you can create an similar outline by 


duplicating the mesh, 
scaling it up a little,
assigning it green shadeless color


(This will not result in a one pixel outline.)