I have a jsfiddle here - http://jsfiddle.net/morettmt/v7mx737w/2/
I can chnage the fill color by styling the grouping
Is there a way to add my own class to the s
Your problem is that the colour from your class style, was being over-ridden by the explicit fill you had on the child element. If you remove that, your CSS works.
class
fill
.triangle{ fill: red; }