Thanks for the compliments on the blends. To be honest though, it isn't as hard as it looks. Yes, there is the use of brush control and understanding glazing, but part of it is just using the right paints for the job.
I basically used phthalo blue (green shade) with lemon yellow. The lemon yellow has white added to it for brightness and opacity and the phthalo blue is a single pigment artist paint. The phthalo blue is transparent, which makes those transitions easy. And that's really the key. If I tried it with a lot of standard mini paints, it would be really frustrating, but you need to understand your pigments.