title: Differing color of points & line in plot.gamm()
body: <p>I ran a GAMM model with a large dataset (over 20,000 cases) using <code>mgcv</code>. Because of the large number of data points, it is very difficult to see the smoothed lines among the residual points in the plot. Is it possible to specify different colors for the points and the smoothed fit lines? </p>
  
  <p>Here is an example adopted from the <code>mgcv</code> documentation: </p>
  
  <pre><code>library(mgcv)
  
  ## simple examples using gamm as alternative to gam
  set.seed(0) 
  dat &lt;- gamSim(1,n=200,scale=2)
  b &lt;- gamm(y~s(x0)+s(x1)+s(x2)+s(x3),data=dat)
  plot(b$gam, pages=1, residuals=T, col='#FF8000', shade=T, shade.col='gray90')
  
  plot(absbmidiffLog.GAMM$gam, pages=1, residuals=T, pch=19, cex=0.01, scheme=1, 
       col='#FF8000', shade=T,shade.col='gray90')
  </code></pre>
  
  <p>I have looked into the <code>visreg</code> package, but it does not seem to work with gamma objects. </p>