var spaceCircles = [30, 70, 110];
 2
 3var svgContainer = d3.select("body").append("svg")
 4                                    .attr("width", 200)
 5                                    .attr("height", 200);
 6
 7var circles = svgContainer.selectAll("circle")
 8                          .data(spaceCircles)
 9                          .enter()
10                          .append("circle");
11
12var circleAttributes = circles
13                       .attr("cx", function (d) { return d; })
14                       .attr("cy", function (d) { return d; })
15                       .attr("r", 20 )
16                       .style("fill", function(d) {
17                         var returnColor;
18                         if (d === 30) { returnColor = "green";
                         } else if (d === 70) { returnColor = "purple";
                         } else if (d === 110) { returnColor = "red"; }
                         return returnColor;
                       });