GUI Texture

I have a GUITexture on an object in the scene and this covers the object completely.
Is it possible to mix a GUITexture with a 3D object in the scene using the channels (Multiply, Screen, etc. …) as in Photoshop?
There is a way to put GUITexture behind 3D object?
The only parameter can I use is the opacity?

This question has been asked several times before. Please do a more thorough search in the future:

http://forum.unity3d.com/threads/119520-How-to-set-GUITexture-behind-of-3d-object