Blackmagic Design has published eight hours of videos that teach you how to edit a video from start to finish inside DaVinci Resolve 15, not just the color grading part of the process. You can get familiar with their tools for VFX and audio processing as well.
The DaVinci Resolve software is famous for two things: it's free and it is so good for color grading. The one drawback has been you have to go back and fourth between your main non-linear video editor and Resolve, exporting and importing projects. Blackmagic Design decided to expand the functionality of their free software making it an all-in-one application. You probably already know you can do basic cuts there, but you may have never got acquainted with their more advanced tools. Although they have hundreds of pages of training materials, users still find their software somewhat intimidating. And no, that's not because their software manuals are badly written. Just the opposite, they are very elaborate and detailed, but not many people like to follow written instructions today. That is probably why the company released video tutorials covering both basic and advanced topics such as color grading.