Simple keychain of a butterfly, but to make the color gradient I used a little trick with the flush volumes, for the blue and white colors I set the purge to 0 from blue to white and from white to blue (see the photo) making that light blue effect, which looks like a gradient of the inner blue.

You can replace the blue color with the one you like the most and make different gradients.

The purge tower is small to aid this effect.