Why Internal-Colored shader working in SetPass posteffect while others are not?

I've been searching for alternatives to "OnRenderImage" method to do a posteffect on mobile platforms and encountered example of one in official documentation here: http://docs.unity3d.com/ScriptReference/Material.SetPass.html

But I've found it working only with mentioned "Hidden/Internal-Colored" shader. Whenever I'm placing there any other shader (Including just-created unmodified NewImageEffectShader) it outputs only one solid color to full screen.

What is the core difference of "Internal-Colored" and why one working in this technique while others are not?