I got some help from Damien Cassou, and he wrote the following code: viewRules: rules view interaction popupText: [:rule | rule ruleName]. view shape rectangle linearFillColor: #counts within: rules; withoutBorder. view nodes: rules forEach: [:rule | self viewRule: rule]. view verticalLineLayout. I would like the colors not to be arbitrary, but to vary depending on the counts value. For example, for a small value, I would like a light color and for a large value I would like a dark color. I could for example normalize the values so that they are between 0 and 100. Is there an easy way to do this? thanks, julia