title: Annotate with shapes outside plot area in specified color
body: <p>I need to annotate my plots in a certain way. Following the answer <a href="https://stackoverflow.com/questions/12409960/ggplot2-annotate-outside-of-plot/12417481#12417481">here</a>, I could come up with this, </p>
  
  <pre><code>df = data.frame(y= rep(c(1:20, 1:10), 5), x=c(rep("A", 20), rep("B", 10), rep("C", 20), rep("D", 10), rep("E", 20),
                                            rep("F", 10), rep("G", 20), rep("H", 10), rep("I", 20), rep("J", 10)), 
              g= c(rep(sample(1:2, 1), 20), rep(sample(1:2, 1), 10),rep(sample(1:2, 1), 20), rep(sample(1:2, 1), 10),
                   rep(sample(1:2, 1), 20), rep(sample(1:2, 1), 10),rep(sample(1:2, 1), 20), rep(sample(1:2, 1), 10),
                   rep(sample(1:2, 1), 20), rep(sample(1:2, 1), 10)))
  
  p &lt;- ggplot(df, aes(factor(x), y)) + geom_boxplot()+            # Base plot
       theme(plot.margin = unit(c(3,1,1,1), "lines"), plot.background= element_rect(color= "transparent"))   # Make room for the grob
  for (i in 1:length(df$g))  {
    p &lt;- p + annotation_custom(
       grob = textGrob(label = df$g[i], hjust = 0, gp = gpar(cex = 1.5)),
       xmin = df$x[i],      # Vertical position of the textGrob
       xmax = df$x[i],
       ymin = 22,         # Note: The grobs are positioned outside the plot area
       ymax = 22)
  }    
  
  gt &lt;- ggplot_gtable(ggplot_build(p))
  gt$layout$clip[gt$layout$name == "panel"] &lt;- "off"
  grid.draw(gt)
  </code></pre>
  
  <p>This generates this plot <img src="https://s32.postimg.org/y8oc37lxx/Rplot.png">.</p>
  
  <p>I want blue triangles with size 0.6 pt instead of 2 in annotation and blue "+" signs instead of 1. Can you please help me out here?</p>