Unable to style colorbar in density mapbox

I am following the example given here: https://plotly.com/r/mapbox-density-heatmaps/

However, I am unable to change the color of the coloraxis (or use showscale = F or move the colorbar over on x).

The plot won't work unless coloraxis = 'coloraxis' is specified, and there doesn't seem to be a way to style the coloraxis.

# population density available from https://data.humdata.org/dataset/worldpop-population-density-for-haiti
pop_den <- read.csv(data_path)
plot_ly() %>% 
  add_trace(
    data = pop_den,  type = 'densitymapbox',  lat = ~Y,  lon = ~X,  z = ~Z,
    coloraxis = 'coloraxis',
    radius = 10) %>% 
  layout(
    mapbox = list(
      style = "carto-positron",
      zoom = 6.5,
      center = list(lon = -73.09, lat = 19.06),
      coloraxis = list(colorscale = "Grey", colorbar_x = 1.5)
      )
    )

Start by reproducing the R densitymapbox example at https://plotly.com/r/mapbox-density-heatmaps/ with the issue's code and inspect how coloraxis and its layout options are handled. Done means the coloraxis color, colorbar visibility, and colorbar position can be styled as requested without breaking the plot.