Continuous colorbar

Hey,
I’m trying to plot the us_states dataset from spData package and fill the polygons by the variable total_pop_15.

tm_shape(us_states) +
tm_polygons(col = “total_pop_15”, palette = “Reds”)


So basically I’m trying to replicate this tmap plot. However plotly always treats the variable as discrete. Does anybody know how I can change that?