title: ggplot2: make the points on the line a darker color than the line color
body: <p>I would like to make each point on the graph a different color from the line. Here is sample data.</p>
  
  <pre><code>df &lt;- structure(list(yrmonth = structure(c(17167, 17167, 17167, 17198, 
  17198, 17198, 17226, 17226, 17226, 17257, 17257, 17257), class = "Date"), 
      index = structure(c(2L, 1L, 3L, 2L, 1L, 3L, 2L, 1L, 3L, 2L, 
      1L, 3L), .Label = c("E-W", "N-S", "OS"), class = "factor"), 
      N = c(2, 2, 1, 2, 2, 1, 2, 2, 1, 2, 2, 1), data = c(129, 
      141, 27, 150.5, 209, 87, 247.5, 243, 188, 223, 226.5, 170
      )), .Names = c("yrmonth", "index", "N", "data"), row.names = 31:42, class = "data.frame")
  </code></pre>
  
  <p>Here is my code for the plot.</p>
  
  <pre><code>df$yrmonth &lt;- lubridate::ymd(df$yrmonth)
  
  ggplot(df, aes(x=yrmonth,y=data,colour=factor(index), group=index)) + 
    geom_line(size=.4) + 
    geom_point(size=1)
  </code></pre>
  
  <p>I would like the green dots to be a darker green, the orange dots to be a darker orange and so forth.</p>