highcharter hc_axis change color of one x-axis label only

[learning-freak]

Hi,
This my dataset

df <- data.frame(dose=c("D0.5", "D1", "D2"),
                 len=c(4.2, 10, 29.5))

I want to change the color of just one label (the label "D1") in red (not all the labels).
I saw this documentation :
https://api.highcharts.com/highcharts/xAxis.labels.formatter
and I tried to do the same thing but nothing has changed

How do I apply style to individual labels to get only the label "D1" in red ?
This is what I did :

df <- data.frame(dose=c("D0.5", "D1", "D2"),
                 len=c(4.2, 10, 29.5))


highchart() %>%
  hc_add_series(
    data = df$len,
    type = 'line'
  ) %>%
  hc_xAxis(categories = df$dose,
           labels = list(
             formatter = JS(
               "
                       function() {
          if (this.value =='D1' ) {
            return '<span style='fill: red;'>' + this.value + '</span>';
          }
          return this.value;
        }
                       "
             )
           ))

Some help would be appreciated

[jsinnett]

You're close but you need to use double quotes and escape them for the style attribute. Also I think 'color' is more appropriate when stylizing text.

highchart() %>%
  hc_add_series(
    data = df$len,
    type = 'line'
  ) %>%
  hc_xAxis(categories = df$dose,
           labels = list(
             # useHTML = T,
             formatter = JS(
               "function() {
                  if (this.value =='D1' ) {
                  console.log(this.value)
                    return '<span style=\"color: red;\">' + this.value + '</span>'; 
                  }
                  return this.value;
                }"
             )
  ))