title: ggplot2: multiple colours in stat_summary
body: <p>I have a plot in which I am displaying individual values from multiple subjects, coloured by group. Added to that are means per group, calculated using stat_summary.</p>
  
  <p>I would like the two means to be coloured by group, but in colours other than the individual data. This turns out to be difficult, at least when using stat_summary. I have the following code:</p>
  
  <pre><code>ggplot(data=dat, 
         aes(x=Round, y=DV, group=Subject, colour=T1)) + 
    geom_line() + geom_point() + theme_bw() +
    stat_summary(fun.y=mean, geom="line", size=1.5,
                 linetype="dotted", color="black",
                 aes(group=T1))
  </code></pre>
  
  <p>Which produces this <a href="http://i.stack.imgur.com/ARCiQ.png" rel="nofollow">example graph</a>.</p>
  
  <p>The colour for the means created by stat_summary is set to black; otherwise it would be red and blue like the individual data lines. However, it is not possible to set more than one colour - so color=c("black", "blue") does not work. </p>
  
  <p>I've already tried scale_colour_manual as explained <a href="https://stackoverflow.com/questions/21817856/how-to-set-multiple-colours-in-a-ggplot2-stat-summary-plot">here</a>, but this will change the colours of the individual data lines, leaving the mean lines unaffected.</p>
  
  <p>Any suggestion how to solve this? Code and data <a href="http://www.simoncolumbus.com/wp-content/2014/10/Analyses.zip" rel="nofollow">here</a>.</p>