Evidently, you can’t have different color aesthetics for two different geoms. As a workaround, use a fill aesthetic for the points instead. This means you have to use a point marker style that has a filled interior (see
?pch and scroll down for the available point styles). Here’s a way to do that:
ggplot() + geom_point(data=merged,aes(x = pauseMedian, y = numTotalPauses, fill = diff), pch=21, size=5, colour=NA) + geom_polygon(data = splineHull, mapping=aes(x=pauseMedian, y=numTotalPauses, colour = microstyle), alpha=0)
colour=NA (outside of
aes()), gets rid of the default black border around the point markers. If you want a colored border around the points, just change
colour=NA to whatever colour you prefer.
Also see this thread from the
ggplot2 Google group, discussing a similar problem and some workarounds.