title: How do I set the color of a single line using ggplot
body: <pre><code>df&lt;-data.frame(adjuster=c("Mary","Mary","Bob","Bob","Mary"), 
             date=as.Date(c("2012-1-1","2012-2-1","2012-3-1","2012-4-1","2012-5-1")), 
             total=c(10,15,25,15,20), paid=c(5,5,10,10,15))
  ggplot(df)+geom_point(aes(x=date,y=total,color=adjuster,group=1))+
    geom_line(aes(x=date,y=paid,group=2,color="Paid"))+scale_color_discrete(name="Legend")+
    geom_line(aes(x=date,y=total,color=adjuster,group=1))
  </code></pre>
  
  <p><img src="https://i.stack.imgur.com/PRTHY.png" alt="enter image description here"></p>
  
  <p>I want to force the "Paid" line to always be black, but let the other lines take the default colors provided by ggplot.  How do I accomplish this?</p>