How to set plotly chart to have a transparent background in R?

Just try:

salesplot <-plot_ly(producersales, type="scatter", x=Producer, y=SalesPerSong, color=SongRange, colors=cols, mode="markers", size=SalesPerSong) %>% 
layout(xaxis = a, yaxis = a) %>% 
layout(plot_bgcolor='rgb(254, 247, 234)') %>% 
layout(paper_bgcolor='rgb(254, 247, 234)') #will also accept paper_bgcolor='black' or paper_bgcolor='transparent'

You can change the rgb numbers to fit your needs.

I find toy need to use rgba AND fig_bgcolor in layout

plt %>%
    layout(plot_bgcolor  = "rgba(0, 0, 0, 0)",
           paper_bgcolor = "rgba(0, 0, 0, 0)",
           fig_bgcolor   = "rgba(0, 0, 0, 0)")