Ass Kick

[Matthew M]

Hey.
First off, awesome work so far. Your drawing is really improving.
Here are a few tid bits that may help you with colour, in no particular order.

Try your hand at some traditional paints. It will improve your eye for colour. I adore Oils, but they can be a bit intimidating at first, and clean up is a pain. Gouache is wonderful, but the colours will dry a slightly different colour.
Complimentary colours will neutralize when mixed. (mix brown/orange to blue to reduce its value/saturation)
Think about values first, colour second; values are what makes an image read, not colour.
Colours are relative. A colour may look different depending on what it's placed next to. For instance, a neutral grey can look warm when surrounded by cool blues. When surrounded by oranges and reds, it can look cold.
Try to avoid colour picking. If you have to, take not of the hue and saturation, then select it yourself. Adjust your other colours relative.
With landscapes, I find it very helpful to separate planes by layer. Sky on one layer, background on another, midground, foreground etc.
Look at the masters. If you're not sure where to start, https://master-painters.tumblr.com/
Focus on learning one thing at a time.
As elements recede into the picture plane, atmospheric perspective makes things become less saturated, higher in value, and shift towards blue.
Things in shadow tend to be more saturated, even if its the same material.
On a sunny day, shadows will tend towards blue.
Try some different brushes in photoshop; there are lots of free brushpacks online
If you're struggling to pick a colour by eye, look at it in isolation. Zoom in until you can see only it. I'll often paint a colour onto the reference to see how close I am. Think value, hue, saturation.
Watch your edges.
You may find that allot of colours are less saturated than you originally thought.

Also, for your anatomy work, take a look at George Bridgman
Best of luck and have fun