There is some ingoing discussions about adding CSS to PlantUML.
See http://wiki.plantuml.net/site/style-evolution
This is not documented yet, but for example with last beta http://beta.plantuml.net/plantuml.jar you can now have:
@startmindmap
<style>
mindmapDiagram {
node {
Padding 5
Margin 15
BackGroundColor white
}
rootNode {
Padding 15
FontStyle Italic
BackGroundColor green
}
leafNode {
Padding 1
BackGroundColor yellow
FontColor blue
FontSize 15
}
}
</style>
* World
** America
*** Canada
*** Mexico
*** USA
<style>
node {
BackGroundColor lightBlue
}
</style>
** Europe
*** England
*** Germany
*** Spain
@endmindmap
Is this what you are looking for ?