How to toggle/highlight interactable items? in many games the items you want to pick change form when you are near or you are aiming at them. Sometimes they change color to a translucent green, sometimes they shine more than the rest objects in the world. I want to create this effect in BGE.

I am working with this buddha statue from GiovanniLucca: statue

In this image: 

you can see what I mean if you notice the desert eagle. There is a yellow highlight.

So how can I achieve this in the statue I am working with? Should I replace its mesh with another one with a different material (highlighted material)? Should I duplicate its mesh and scale it a bit to be close to the original and then change the color of the outer mesh and animate it to change from let's say transparent to green translucent when I am aiming at it? Is there another way? Has anyone done it?

I just want the player to know with which items he can interact and with whom he can't. I tried replacing meshes with transparent materials(in the whole object) and I was disappointed with the result.

Edit: I wasn't quite clear cause I did not know the way to do this I guess. My question is, how can I re-create the effect that you see in the image around the gun(desert eagle)? When the character is near I want it to get highlighted like this. The logic-bricks-code are done to detect when the character is near. So, how can I make it emit this (yellow) light close to its faces only and keep its textures still visible?
Duplicate Mesh Outline

Have a mesh to be outlined:




shift+d to get a copy of the object and the mesh (give it
appropriate names) 
ut: Make Single User "Materials + Tex", to get
separate materials (give them appropriate names)
tab enter edit mode
select all vertices 
alt+s fatten the mesh e.g by 0.1. The resulting mesh should be larger than the original. 

w + flip normals to make the faces show inside
tab to leave edit mode


As the outline should have an "aura" effect, I suggest to chose a shadeless material with "Add" Alpha. The color should be pretty dark. Otherwise it will hide the background too much.



This results in a semi-transparent "glowing" effect. 

While it looks strange in the preview the game engine will show you a nice outline.

 

PS: Thanks to Satish Goda (youtube) I know now how to enable backface culling. Therfore I suggest following additional settings:


parent the hover to the original object
make the hover unselectable
 in Properties enable Shading/Backface Culling




This is the effect. Now you can think about logic that switches it on and off. 

Hint: you can even fade it by playing material actions.

I hope it helps