I recently ran across this video on YouTube. It's a nice primer on color theory and how it related to paint mixing. I was surprised at how well it covered the subject in a way that I felt really applied directly to what I do with miniature painting.
Of course, it's not that I don't know this stuff. I do. But sometimes it's nice to get a refresher on the basics. I've noticed that I sometimes get into a rut with painting where I will tend to paint certain colors in certain ways or grab from the same palette no matter what I'm painting. Sometimes going back to basics can inspire my mind to give more thought to what I'm doing before I do it.
On the other hand, keeping this information at the top of your mind will help when you're stuck thinking about the best way to highlight or shade something. This is especially true when you don't have just the right pre-mixed shade that you're looking for and you aren't quite sure what the best way to mix what you want would be.
I have a lot of books and magazines on painting and modeling. They are great to break out and look through every now and again to get the old creativity brain cells firing again. You can always pull out some new technique that you had read about before, but it had never been relevant to you previously. Of course, these days YouTube tends to fill this niche for me more often. I have many good painters on modelers on my subscription list. Even if I'm not actively paying attention to them as I paint it's nice to have that running commentary going on in the background for my mind to sift through as I'm working on a project.
If there's a point to this all, it's that it's good to keep learning as well as re-learning. You never know what bit of information is going to be helpful on your projects.