Attach it to an object at the top level of your project hierarchy. This could be a GameObject instance, or an instance of the ARCamera.

Post a snippet of the code you're using if you still have trouble.

Tank you for your answer David.
I try to use code from unity forum but without success.
Make a new Mono script with code from Unity forum but where I must put the script. On imageTarget prefab? On object mesh into prefab?

Tank you

Here is a thread on the Unity forum that demonstrates a few methods for accomplishing this - http://forum.unity3d.com/threads/51117-Change-color-of-an-individual-Game-Object

So you are either affecting the material color, or the vertex colors on the mesh.

To accomplish this interactively, simply execute these methods from the appropriate event handler.

Hi David,
sorry for my imprecision (and for my english).
The question is how to change color of the model in the app, when target is detect and model is show by app.
I would change color of an object interactively with a screen touch or with an interface button.
It is possible?

Tankyou

To change this procedurally, or simply to change the color in Unity?

To change this in Unity, you can alter the material and texture properties in the Inspector.