A modifier, not a base coat itself.
The design has two other colors of your choice as modifiers, similar to the other legendary bases. Must be same or lower rarity than the base coat it comes with.
Calico must show all three colors on the Tally in some way and cannot have extra colors that are rarer than the base coat. Thus, a Calico Raven, Waterlogged, or Tainted would show all three in some way, a Calico Albino can show effects of those or Nighted and vice versa, and a Calico Crimson, Fruity, or Golden can show two more of any color. (Skinned/Bloodstained and Neon/Silver can still affect this, meaning all three colors would have to be light/dark or saturated/desaturated respecively.)