title: How to manually fill colors in a ggplot2 histogram
body: <p>I am generating a histogram and I would like to color certain groups with specific colors. Here is my histogram:</p>
  
  <p><img src="https://i.stack.imgur.com/5PIRO.png" alt="enter image description here"></p>
  
  <p>I have 14 groups and I would like to color the first 7 red, the next 4 blue, and the final 3 orange. How can I do this in ggplot? Thanks.</p>