I feel like I see a lot of color palettes where the blue and green meet at the dark end (low luminosity).  While it makes sense that you can use that color for the shading of both blues and greens it contradicts what I've read in typical hue-shifting: blues get more purple as they get darker and more cyan as they get lighter.

Is this a "there are no rules" scenario where it is however you can make it work?  Is it common for palettes to have blue and green to meet at high luminosity?


Note: purpose is to better understand how to make color palettes where colors work together well, which I'm struggling at.