I create pixel assets and sell them on itch.io as asset packs. Usually, if the asset is something that could come in multiple colors, like animals or furniture, I try to include a few color variations in the pack. Typically, I do maybe two or four variations, but should I make it standard practice to offer more? I'd love to hear any insights you may have

Color variations are great to have especially for objects which naturally could come in different colors such as toys, foods and clothes. Not to mention, the default color may not be liked but the alternate color may be liked more.

TLDR you should make it a standard practice.

If I were going to use other people's graphics, I'd swap colors to my preferred palette with PixelPaletteTool.

 https://withthelove.itch.io/pixelpalettetool

BTW, your work is inspiring. I really like your birds. Thank you.

As a user of pixel art assets, I usually end up changing the colors anyway for consistency with my other art.