make everything inside a collision box have outline

so i got a little problem i have no clue as to how to the desired effect.

lets say i have 5 objects inside one bigger collison box now i want each and everyone of these objects to have a outline when you mouse over the collisionbox not each object but the Box that everything is inside.

is it possible if so can someone guide me in a direction?

i know of shaders but i just dont know how to do it with them yet. still novice on shading