Crystal chart, colour highlight by 3rd element

Question

Hi all, What I'm trying to achieve seems fairly simple but I've not come across a way to do it. I'm trying to create a chart using 3 elements:

string 'Vehicle'
int 'Number of Vehicles'
bool 'Is Van'

So basically the string and int represent the x/y values and the bool is needed to shange the colour of the bar chart. If the vehicle is a van it should show a blue bar, if not a red bar.

Sounds easy enough, just need to know how?

Cheers :)