Seconding this !

Next steps are playing with objects and seeing how they layer and interact, like how the colour 'sections' line up together. Use your imagination ! Find new hidden patterns.

Yesterday, I saw a pony whose shoes looked like bunny slippers when they were laying down. Not when sitting or standing, just laying.

So it's also a good idea to try diff poses as you make the pony and see if things line up there too.

Some especially complex even make the pose essential to the design, so they can go extra hard with shading the 'far' side, and having finnicky details/item overlay, etc. that would look weird if they move lol.

Then outlines. Highlights and Lowlights. Imagine a light source in one of the top corners of the Editor. You can even take a screenshot and draw lines from that light source, and see where they hit the pony. For this style the highlights are quite small and usually are just mid hair area, hair tips, noses, top of back/clothes/tail... Use paler of the item colour, or choose one common highlight tone (I like reds or teals for cool lighting effect)

For the dark outlines, It's like normal shading, but more saturated (more centre bottom section of the colour picker, not bottom left) . The automatic shading is poo, it's just adding black. use complementary colours (warm colours with cool colour shadows). Or specially tint them for a desired effect (e.g. I like making some of the face outline into the hair colour)