Feature Request: plotter: add the ability to change the colours with discrete (tcl) colour

[tremblap]

Is your feature request related to a problem? Please describe the problem.

as per https://discourse.flucoma.org/t/fluid-plotter-documentation-colour-message-method/2736/2

Describe the solution you'd like to see.

changing each point's colour, and also the colours of the respective classes maybe.

Describe alternatives you've considered

switching to javascript

Additional context

I hate this form