title: Changing line colors with ggplot()
body: <p>I don't use ggplot2 that much, but today I thought I'd give it a go on some graphs. But I can't figure out how to manually control colors in <code>geom_line()</code></p>
  
  <p>I'm sure I'm overlooking something simple, but here's my test code: </p>
  
  <pre><code>x &lt;- c(1:20, 1:20)
  variable &lt;- c(rep("y1", 20), rep("y2", 20) )
  value &lt;- c(rnorm(20), rnorm(20,.5) )
  
  df &lt;- data.frame(x, variable, value )
  
  d &lt;- ggplot(df, aes(x=x, y=value, group=variable, colour=variable ) ) + 
              geom_line(size=2)
  d
  </code></pre>
  
  <p>which gives me the expected output:</p>
  
  <p><img src="https://i.stack.imgur.com/xN5gh.png" alt="enter image description here"></p>
  
  <p>I thought all I had to do was something simple like:</p>
  
  <pre><code>d +  scale_fill_manual(values=c("#CC6666", "#9999CC"))
  </code></pre>
  
  <p>But that changes nothing. What am I missing?</p>