title: Missing color when plotting a raster
body: <p>When I try plotting a Raster object, R gives a plot without colors. </p>
  
  <pre><code>library(raster)
  r.base &lt;- raster(ncol=40,nrow=40,xmn=-74,xmx=-34,ymn=-34,ymx=6)
  wgs&lt;-"+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"
  projection(r.base) &lt;- wgs
  set.seed(0)
  values(r.base) &lt;- runif(ncell(r.base))
  plot(r.base)
  </code></pre>
  
  <p>Code runs on a Windows server with R3.3.0, resulting in: 
  <a href="https://i.stack.imgur.com/UY9Ht.jpg" rel="nofollow noreferrer">Plot without color</a></p>
  
  <p>On a private computer the plot funciton works fine, resulting the intented output:
  <a href="https://i.stack.imgur.com/qmAM4.jpg" rel="nofollow noreferrer">Plot with color</a></p>