How to apply an CSS style on a mindmap node to change color ?

[louxyy]

Hello everyone,

I am discovering the midmap diagram. This kind of diagram is very interesting, helping to better visualize the ideas of my note.

However I find the color too much garish.

So would be it possible to change the color like on flowchart ?

    mindmap
      root((mindmap))
        Origins
          Long history
          ::icon(fa fa-book)
          Popularisation
            British popular psychology author Tony Buzan
        Research
          On effectiveness <br/> and features
          On Automatic creation
            Uses
                Creative techniques
                Strategic planning
                Argument mapping
        Tools
          Pen and paper
          Mermaid

The render :

How can I change the green node ?
For example, I have this class with a less garish green color that I used on a flowchart diagram
classDef green fill:#568203

Where should I put the class declaration ? I tried it before "Tools" node but my class declaration is interpreted as a node. If I put it the root node, I get an parsing error telling that there can be only one root.

    mindmap
      root((mindmap))
        Origins
          Long history
          ::icon(fa fa-book)
          Popularisation
            British popular psychology author Tony Buzan
        Research
          On effectiveness <br/> and features
          On Automatic creation
            Uses
                Creative techniques
                Strategic planning
                Argument mapping
        classDef green fill:#568203
        T["Tools"]:::green
          P["Pen and paper"]:::green
          M["Mermaid"]:::green

The mindmap is an experimental graph, maybe it hasn't been implemented yet in a stable way, or maybe I've made a syntax error.
I didn't see the class declaration in the documentation example : https://mermaid.js.org/syntax/mindmap.html