how to hightlight a treenode if tree lose focus

[C# Programming]

you know, select a tree node, it would be highlighted with blue color, if the tree lose focus, the color would be gray, it's hard to know which one is selected, is there a good way to change the gray to a light color? Or need to redraw the node?
if need to redraw the node, there would be many works need to do, like restore the node etc.
Is there a good sample to show this?

Thanks you!