title: rgb transparent colors in plotly and R
body: <p>I am trying to get a plotly graph with a filled area that is semi-transparent purple. I can find the rgb designation fine and get it to work in a simple plot. But it seems that plotly doesn't read in rgb's the usual way?</p>
  
  <pre><code>plot(rnorm(10),col="#A020F066",pch=15,cex=13)
  # plots squares that are transparent purple (expected)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/draij.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/draij.png" alt="plot with purple squares"></a></p>
  
  <pre><code>p=plot_ly(x=c(1,2,3,4),y=c(1,2,5,10),type="scatter",line=list(color="red"))
  p=add_trace(p,x=c(1,2,3,4),y=c(11,12,15,20),type="scatter",
          fillcolor="#A020F066",fill="tonexty",
          line=list(width=10),marker=list(size=10))
  p
  # plots area that is transparent mint green (What? I expected purple)
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/UUZdf.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/UUZdf.png" alt="plot with green fill"></a></p>