Dispose Of Brush When Using SystemColors.xxxx As The Color?

So, reading around varous places, (MSDN, these forums, CodeProject etc.) it's clear that you should dispose of any Pen's, Brushes etc. that you create and that perhaps the best way is via aUsing block. But some behaviour has confused me and I think it might be related to the color I use when I create the Pen / Brush (read this in a post in the C# forums).It now works since I've used a Using block to replace the Dim....Dispose() shown below. But I don't understand why because all the Using block does is ensure that the used object is disposed of. It's just short-hand for Dim....Dispose() - at least that's what I understand