you need to shift the hues and saturation a bit, not just lightness. Colors are more towards yellow when lit and closer to blue/purple when in the shadow. Look at your favorite games or whatever pixels you like and see how those colors are picked. If you're using paint you probably can't see the HSL for picked colors (from what i remember) so try some other programs.
also black outlines don't always look good, especially if the sprite is small and you outline everything