title: How to change the font size of the tick labels in contour plot colorbar in R?
body: <p>I am using <code>plot_ly</code> to plot a contour plot. The code is as follows: </p>
  
  <pre><code>X = c(1, 2, 3, 4, 5, 6)
  Y = c(seq(from = 1, to = 17, by = 1))
  Z = matrix(runif(17*6), ncol=17)
  m &lt;- list(colorbar=list(title = "hi"))
  plot_ly(
    x = X, 
    y = Y, 
    z = t(Z), 
    type = "contour",
    opacity = 100,
    fillcolor = "FALSE",
    line = list(width = 1.5),
    contours = list(showlabels = TRUE, 
                    labelfont = list(size = fs, color = 'white')), 
    color = I('black')
  ) %&gt;%
    layout(xaxis = list(title = "X", titlefont = list(size = fs), 
                        ticktext = c("9:00", "9:30", "10:00", "10:30", "11:00", "11:30"), 
                        tickvals = c(1, 2, 3, 4, 5, 6), 
                        tickmode = "array", 
                        tickfont = list(size=fs)),
           yaxis = list(title = "Y", titlefont = list(size = fs), 
                        ticktext = c("0", "30", "60", "90", "120", "150", "180", "210", "240", 
                                     "270", "300", "330", "360", "390", "420", "450", "480"), 
                        tickvals = c(1:17), 
                        tickmode = "array",
                        tickfont = list(size=fs)))
  </code></pre>
  
  <p>The output I get is:</p>
  
  <p><a href="https://i.stack.imgur.com/dzsBu.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/dzsBu.png" alt="contour plot"></a></p>
  
  <p>How do I change the font size of the colorbar tick labels (encircled in red)?</p>