NGUI Button isEnabled does not work BUG

Yeah,
If you set isEnabled = false of a UIButton in NGUI, the color of the button does not change even it is disabled.

It is a bug actually, you should change the NGUI isEnabled source code as follows:

public bool isEnabled
    {
        get
        {
            if (!enabled) return false;
            Collider col = collider;
            return col && col.enabled;
        }
        set
        {
            Collider col = collider;
            if (col != null) col.enabled = value;
            else enabled = value;
            UpdateColor(value, false);
        }
    }

Here is the link:
http://www.tasharen.com/forum/index.php?topic=6893.msg32520#msg32520

Note:
This bug is fixed after 3.x version, not sure which exactly.