title: Changing color of density plots in ggplot2
body: <p>I've got a nifty pair of probability density functions I created with ggplot2 as follows:</p>
  
  <pre><code>require(ggplot2)
  set.seed(2)
  data &lt;- rbind( data.frame(type="a", lr=rnorm(100)), data.frame(type="b", lr=rnorm(100,.5,1.2)))
  m &lt;- ggplot(data, aes(x=lr)) 
  m &lt;- m + geom_density(aes(fill=factor(type)), size=2, alpha=.4) 
  m
  </code></pre>
  
  <p>and that produces a nice plot:</p>
  
  <p><img src="https://i.stack.imgur.com/2EgbR.png" alt="enter image description here"></p>
  
  <p>However I would really like that plot to have different color shading. I can't seem to figure it out. I thought the following would work:</p>
  
  <pre><code>m + scale_colour_manual( values = c("red","blue"))
  </code></pre>
  
  <p>But no luck. I also tried passing fill colors to the geom_density() call, to no avail. </p>
  
  <p>How do I change the fill colors? </p>