for color schemes u can try lookin at a color wheel for ideas
i usually pick my outline color first, and try to make it a dark shade
so like, if i outline it with a green marker (like a green thin sharpie)
then i usually do the fill with different, lighter shades of green,
then i color the 3D the same as the outline, and then i try to pick a color for the aura that will
contrast well against the greens, like something bright and vibrant