One thing I always love to discuss is pushing the range of one color as far as possible... in multiple directions at once. That is, warmer/cooler, saturated/muted, darker/lighter and so on.
Here's a sample video that I made for the original Painting Pyramid series of tutorial videos. I will certainly be creating some new versions of these for the Patreon Page!
What registers as "Green" to the eye can be many different things. Potentially a muted greenish gray could convince the eye that it is a 'dingy green' by placing a deep, dark red next to it. As the say, everything is relative!
Even contrasting very warm bright greens against darker, blueish greens creates a nice depth of color, even though it is all technically green. Once you add in that element of 'graying down' the green by adding reds to the mix, or by placing other reddish browns near it, you have a lot of interest in what would be considered a narrow band of colors.
While my regular 2D art background is primarily the reason I think this way (due to the use of 6-8 colors at most on a given painting), using fewer colors while painting miniatures leads to more adventures in mixing and playing the colors off of each other.
By the way, yet another fantastic Dark Sword sculpt! Be sure to check out the Patreon Page, because even more tutorial videos will be added now that the first goal have been achieved! Many thanks to Dark Sword, and all those who have helped make these possible with their support!