MouseOver Effects
MouseOver effects are the special effects triggered when the mouse pointer moves over a node. The effects are grouped into 3 categories.
Default Effects
Default effects are MouseOver effects that appear when you set activeStyle="none". Basically no border appears around the active node, but the node's caption is highlighted. You can control the colors as well as font style of the active node's caption.
Here's an example where the active node's caption is set to red:

Here's an example where the caption's font style is set to fsItalic:
2D Effect
- Square Rectangle Border - A colored square rectangle appears around the active node:

- Filled Square Rectangle Border

- Rounded Rectangle Border

- Filled Round Rectangle Border

- Oval Border

- Filled Oval Border

3D Button Effect
3D button with active3DButtonBevelHeight=5

3D button with active3DButtonBevelHeight=2

3D button with active3DButtonBevelHeight=5 with a different combination of light and dark shade colors
3D Text Effect
You can make the active node's caption pop out in a 3D fashion as follows:

With a different shade color...

And with a different bevel height (originally set to 5, now set to 3):
You can also set the default nodes to 3D by setting default3DNodes="yes":