Thanks for the compliment, Ann--I’m sure you could find many better examples.
I don't know that there are any short, easy secrets I could sum up in a single favorite tip. As far as “magic” colors: in addition to the basics, two I added aawhile back are Quinacridone Red and Chromium Green (oils). Both are strong and less prone to becoming muddy when mixed. Another painter I know is a big fan of Gamblin’s Transparent Orange (again, oil.) I don’t like it much for opaque painting (might as well use the stronger Cadmiums), but for tinting and glazing (which I generally try to avoid), it can be magical for warming things up.