title: Overplotting with different colour palettes in ggplot2
body: <p>Dear stack overflow readers,</p>
  
  <p>I am having a dataset for which I have "raw" data and for which I additionally compute some kind of smoothing function for. I then want to plot the raw data as points, and the smoothing as a line. This works with the following:</p>
  
  <pre><code>Loc &lt;- seq(from=1,to=50)
  Loc &lt;- append(Loc,Loc)
  x &lt;- seq(from=0,to=45,by=0.01)
  Val &lt;- sample(x,100)
  labels &lt;- NULL
  labels[1:50] &lt;- 'one'
  labels[51:100] &lt;- 'two'
  
  x2 &lt;- seq(from=12,to=32,by=0.01)
  Val2 &lt;- sample(x2,100)
  raw &lt;- data.frame(loc=Loc,value=Val,lab=labels)
  smooth &lt;- data.frame(loc=Loc,value=Val2,lab=labels)
  
  pl &lt;- ggplot(raw,aes(loc,value,colour=lab)) + geom_point() + geom_line(data=smooth)
  print(pl)
  </code></pre>
  
  <p>The result looks like this:</p>
  
  <p><img src="https://i.stack.imgur.com/VJQeU.png" alt="enter image description here"></p>
  
  <p>The problem is that my actual data contains so many data points that using the same colour palette is going to be very confusing (the difference between point and line will be almost indistinguishable). Preferably, I would make the geom_lines() slightly darker. I've tried with <code>scale_colour_hue(l=40)</code>, but that results in the the geom_points() to be darker as well. </p>
  
  <p>Thanks for any suggestions!</p>