The way false colour works is by separating different levels of IRE into colours, so you can determine what is over or under exposed by the colour that it appears. Different monitors have different colour schemes, so make sure you know which colours mean what on your monitor, but the aim is to get your skin tones to 70% IRE. This video breaks it down and simplifies it for you, and will help you understand IRE if you aren’t sure what that means.