When using the base R graphics in a shiny app I tried to make the background of my plots dark so I invoked
par(mar = rep(0, 4), bg = "black", fg = "white")
before calls to the plotting functions. On my desktop in RStudio it all works as expected but when pushed to an instance of shiny server the bg parameter is not respected while the fg parameter is! The plot background remains white. You can see this in action (at least until you show me my errror!) here, on the opening screen. This problem doesn't exist with ggplot themes, FWIW.
Thanks for ideas how to fix this.