Fix the colors in Treemap chart

Hi all,

I'm new here and I begin to use Pentaho:) , so I need you please...
My problem is to fix colors for each category in TreeMap chart.
For eg:
I have 2 categories of car : BMW and VW and for each category I have many types of car;
BMW: Serie1, Serie2....
VW: Golf, Jetta, Passat....

So, I would like to fix colors for this two categories: BMW and VW (all BMW in blue and all VW in red).
I used many things but nothing :(, I can't fix the colors!

I use also in Pre Execution, in Post Excution, in Post Fetch, in Pre Change, Post Change:

function f() { // Series Value => Fixed Color
this.chartDefinition.colorMap = {
"BMW": 'blue',
"VW": 'red'
};
}

But nothing

Thank you for help!!