You can do this using "StackedColumns". The idea is that you can create one serie per each color. For example, a "green" serie for values <=5, other for values >5 and <=10 and "red" for values >10.
Then, you have to evaluate each value in the array that you have the data, and put that value in the corresponding serie, like this:
for(var i=0; i<chartData.length;i++){
if(chartData[i]<=5)
fill("green",chartData[i]);
else if(chartData[i]>5 && chartData[i]<=10)
fill("yellow",chartData[i]);
else
fill("red",chartData[i]);
}
See this jsfiddle to see the example running using dojo