Hey! So cool illustration! Really like it so far! :D So... I don't know if you want to avoid getting muddy colours. By definition, we refer to muddy colours when we have lost the vibrancy between our colours. The colours on your painting might appear dull, lifeless or lacking in vibrancy. However, I was reading a blog about this, and I found something interesting that I'd like to share it with you. We can break this theme down into muddy, chalky, or flat, which are just three different words all describing this theme. 'Muddy' was what he used to describe warm-warm paintings (that is, warm colours next to warm colours next to warm colours), chalky for cool-cool paintings, and flat to describe paintings that have too similar values (which, in my understanding, we can understand as "muddiness", the lack of values). Having this in mind. The picture feels "muddy" since everything is too warm, and you need cool colours to add more vibrancy. So that's why I added some blue tones at the bottom to keep that relation between warm and cool. I also adjusted the values a bit by adding more brightness at the top :) You need to practice a lot and study people who did it well, either old masters or actual illustrators. Analyze how they use colours to avoid what I've talked. You can also read "Color and Light" by James Gurney for a better understanding of colours in general. Hope this helps!
