Hey Brendin - this is a great question! There are a few different types of colorblindness. Deuteranomaly - reduced sensitivity to green - is the most common, affecting about 5% of the male population. All told, around 8% of males and 1% of females the world over have some form of colorblindness, meaning that almost 1 out of every 10 site visitors will suffer from this. This is the biggest argument I give about why sites need to put accessibility first - would you be willing to lose 10% of your customers with a design decision that is easily fixed? Probably not.
Plugins like this are great helpers to uncover colorblindess accessibility issues. In my class on UX Accessibility I host on Skillshare, I have a UX Accessibility Toolkit with some helpful links to review for colorblindness and other accessibility concerns. You can get access to the toolkit, the class, and 2 free months of Skillshare premium by signing up here: http://skl.sh/2BISYLj (forgive my shameless plug).