OnMouseEnter of two overlapping quads

I have one quad overlapping another quad in my game. Is there a way to only trigger the OnMouseEnter function of the quad that is rendered later? What mesh should I select for the mesh colliders of these two quads?

I have solved this by setting gameObject.layer.
Can I enable/disable a collider so it will/won't detect mouse clicks? - Questions & Answers - Unity Discussions would help if you have similar problem.