Reference layers are a game changer for anyone who does digital art. Reference layers allow us to make some aspects of the digital coloring process a lot easier.
Many beginning digital artists make a mistake when starting to add color to their art. Once they have some nice inks down, they grab the bucket fill tool in whatever software they're using and start adding color willy-nilly to the same layer that their line art is on. This produces results like the following screenshot:
If we look closely at the area between the black lines and the color, we can see a slight line of white and gray pixels that haven't been filled ...