実行時にシェーダを差し替える ref: http://qiita.com/snaka/items/f7065604ce7306282821

file0.txt

        // change shader
        var defaultShader = Shader.Find ("Sprites/Default");
        var renderers = ((GameObject)instance).GetComponentsInChildren<SpriteRenderer>();
        foreach (var r in renderers) {
            r.material.shader = defaultShader;
        }