in toolkit/jb/svg.js [529:536]
function addColorRect(parent, color, size) {
return d3.select(parent).append('rect')
.attr('width', size || 7).attr('height', size || 7)
.attr('rx', 1).attr('ry', 1)
.attr('fill', color || 'transparent')
.attr('stroke-width', 0.5)
.attr('stroke', 'white');
}