title: Adding a legend to a ggplot - invalid color name
body: <p>I have looked around in the documentation and posts like <a href="https://stackoverflow.com/questions/17148679/ggplot2-need-to-construct-a-manual-legend-for-complicated-plot">this</a>, but it is not clear to me. Apparantly a legend is created automatically and I have to map colors to explaining text. </p>
  
  <p>An example with data:</p>
  
  <pre><code>vtm1&lt;- c(1,3,4)
  vmean&lt;-c(3.9,3.8,3)
  vmax&lt;-c(4.1,4.2,4)
  vmin&lt;-c(3,2.5,2)
  rtm1&lt;- c(1,2,4,5)
  rmean&lt;-c(3.9,3.85,3.7,3.1)
  rmax&lt;-c(4.1,4.2,4,3.9)
  rmin&lt;-c(3,2.5,2,1.9)
  gtm1&lt;- c(2,4,5)
  gmean&lt;-c(4.1,3.9,3)
  gmax&lt;-c(4.1,4,3.9)
  gmin&lt;-c(3,2.5,1.5)
  vns &lt;- data.frame(vtm1, vmean, vmax, vmin)
  gibbs &lt;- data.frame(gtm1, gmean, gmax, gmin)
  rw &lt;- data.frame(rtm1, rmean, rmax, rmin)
  
  plt &lt;- ggplot(NULL, aes(x= vtm1))
  plt + xlab("Number of TM lookups") + ylab("Cross-entropy") + 
  xlim(0, 30000000) + 
  ylim(3.15,4.2)+  
  geom_ribbon(data=gibbs, aes(x = gtm1, ymin= gmin, ymax= gmax), fill="#A8A8A8") +  
  geom_ribbon(data=rw, alpha=0.5, aes(x = rtm1, ymin= rmin, ymax= rmax), fill="red")+  
  geom_ribbon(data=vns, alpha=0.5, aes(x = vtm1, ymin= vmin, ymax= vmax), fill="mycolor")+ 
  geom_line(data=gibbs, linetype = "dotdash", aes(x=gtm1,y=gmean)) + 
  geom_line(data=vns,aes(x=vtm1,y=vmean)) + geom_line(data=rw, linetype = "dashed", aes(x=rtm1,y=rmean)) + 
  geom_hline(yintercept=3.2240952381, linetype = "dotted", color="mycolor2")+ 
  geom_hline(yintercept=3.44366666666667, linetype = "dotted") + 
  theme_bw( )+
      scale_colour_manual(name="Lines", values=c("mycolor"="blue","mycolor2"="red")) +  
      scale_linetype_manual(name="Lines", values=c("mycolor"="dotted","mycolor2"="dashed"))
  </code></pre>
  
  <p>R keeps giving me the error: </p>
  
  <pre><code>Error in col2rgb(colour, TRUE) : invalid color name 'mycolor'
  </code></pre>