How can I color code for two different variables? Currently I alter the opacity:
scale_alpha_manual(values=c(1, 0.5), labels=c("net sales", "contribution margin"),name = "Opacity") + # opa
So the 2nd bar in the chart is always a little transparent. However what I would really like to have is the 2nd (and following) bar(s) in a group to be gradually darker / brighter versions of the first one without introducing transparency.