1. Everytime I import Vuforia into a clean project I get
Assets/Vuforia/Scripts/WireframeBehaviour.cs(41,24): warning CS0618: `UnityEngine.Material.Material(string)' is obsolete: `Creating materials from shader source string will be removed in the future. Use Shader assets instead.'
2. Much larger issue
Building for android 5.1 in unity 5.1.3 (unsure if issue exists in iOS as I havent tried) i get flickering rgb tinted buttons when I have Vuforia enabled. It goes away when I delete the asset. The only way to get rid of them is to enable development mode, which obviously isnt realistic for production versions. I have the asset https://www.assetstore.unity3d.com/en/#!/content/14656 which when enabled, I assume also creates a form of debugging, becaue it also removes the issue, but again, i dont want fps counter on my production app, just to fix the issue your software is creating.
On some occasions after restarting unity the issue goes away unless I turn on MultiThreaded Rendering. On my Samsung Tab2 the opposite works and requires the MultiThreaded to be on, otherwise the same issue occurs. So unless I enable dev mode, I cant get it working on both devices properly.
Issue exists in your sample scenes as well
I have attached a screenshot that illustrates the issue