You might, for example, color all cues that still need their audio to be recorded as red.
Or, you might, for example, color all video cues blue and audio cues orange.
Or, you might, for example, color each row in the order of a rainbow because that makes you happy.
You can do whatever you want. To specify a color, select your cue and pick one of QLab’s 5 colors. Only 5 colors? Well … be honest … how much time would you waste choosing if you had more choices. The 6th option, the X, is no color. And here’s a secret you can actually pick more colors but I’m gonna have you google that to figure that out on your own.
What is the proper way to color your cues?
There isn’t one! Whatever works best for you and your design process.