R Barplot continuous colour

Hi - quick question, I’d like to have a continuous colour scale on an R plotly barplot - it only seems to work with discrete factors - is this possible?
Here’s an example of what I’d like to have (contrived, I know - but you get the gist)
plot_ly(iris, x = Petal.Length, y = Petal.Width, color = Sepal.Length, type=‘bar’, orientation=‘h’)
Scatterplots have it:
https://plot.ly/r/user-guide/

For everyone else’s information: I got a reply on plotly chat - this is not possible currently in R plotly (or I believe plotly itself)