title: How to change the color palette for GGally::ggpairs?
body: <p>This is the same question as in
  <a href="https://stackoverflow.com/questions/22237783/user-defined-colour-palette-in-r-and-ggpairs">User defined colour palette in R and ggpairs</a> or <a href="https://stackoverflow.com/questions/14711550/is-there-a-way-to-change-the-color-palette-for-ggallyggpairs-using-ggplot">is there a way to change the color palette for GGally::ggpairs using ggplot?</a></p>
  
  <p>only that the solutions there don't work anymore.</p>
  
  <hr>
  
  <p>I also want to change the color palette, but <a href="https://stackoverflow.com/questions/14711550/is-there-a-way-to-change-the-color-palette-for-ggally-ggpairs-using-ggplot">is there a way to change the color palette for GGally::ggpairs using ggplot?</a> does not work anymore. What to do?</p>
  
  <p>MWE:</p>
  
  <pre><code>library(GGally)
  library(ggplot2)
  data(diamonds, package="ggplot2")
  diamonds.samp &lt;- diamonds[sample(1:dim(diamonds)[1],200),]
  ggpairs(
    diamonds.samp[,1:2],
    mapping = ggplot2::aes(color = cut),
    upper = list(continuous = wrap("density", alpha = 0.5), combo = "box"),
    lower = list(continuous = wrap("points", alpha = 0.3), combo = wrap("dot", alpha = 0.4)),
    diag = list(continuous = wrap("densityDiag")),
    title = "Diamonds"
  )
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/tbFGh.png" rel="noreferrer"><img src="https://i.stack.imgur.com/tbFGh.png" alt="enter image description here"></a></p>
  
  <p>I would like to add</p>
  
  <pre><code>scale_colour_manual(values=c('red','blue','green','red','blue'))
  </code></pre>
  
  <p>(obviously that is just dummy code) and get something like (I did not paint over all the dots):</p>
  
  <p><a href="https://i.stack.imgur.com/v3AyX.png" rel="noreferrer"><img src="https://i.stack.imgur.com/v3AyX.png" alt="enter image description here"></a></p>