尝试在ggplot中的直方图上应用颜色渐变

I am floundering with colors in ggplot. I am trying to apply a color gradient based on the rank column below. I am pretty sure this is a discrepancy between color and fill or discrete and continuous variables. I want colors as shown on the scale in "c" and "d" below, but my closest attempts are "e" and "f" where the points are colored but not colored by gradient. The gradient I prefer applies to values of rank 1:100, with all others values' points black. I am floundering with colors in ggplot. I am tr