Long answer ahead!

I find that an easy way for me to come up with a palette is to stick with one "main" colour. I get lots of colour inspo from other artworks and photography.

-Slowly start adding other hues to complement that main colour. This is where colour theory knowledge comes in. Know your complimentary and analogous colours.

-Don't be afraid to choose lots of beautiful neutrals in your artwork, the more neutrals you have, the more your bright colors will pop! If you have the means to, i find that practicing traditional paint colour mixing with primary colours helped me deepen my understanding of neutrals.

-Use varying hues of the same colour family. This is a good way to introduce lots of colour to your piece without having a messy colour scheme. If you're working digitally, you can tweak your brushes to include colour jitter for more hue variation.

-If working digitally, make use of layer modes and gradient maps to amplify your colours. My favorite layer modes are Overlay, Brightness, Colour burn, and Add(glow). If you're a csp user, you can log in to csp assets to download gradient map packs created by other users. I like to stack up my gradient maps to have more unique effects.

Good luck ٩(•ᴗ•)۶