When Ash and Co. traveled around the Orange Islands in the Pokémon anime back in 2000 they stumbled upon a strangely colored Butterfree. While Butterfree is typically known for having white wings, this one had yellow wings with an orange spot. While the orange is much more pronounced on the real world Kamehameha Butterfly of Hawaii (named after the Royal House of Kamehameha, and not the Dragon Ball move), it would be an interesting design change.
This new Butterfree could take on an Electric/Bug typing or maybe Fire/Bug. As for the reason it took on this coloring, it could be that it was crossbred with the Archipelago Vivillon from Pokémon X and Y. It's a bit of a stretch, but it could be a result of an offering to the royalty of Alola, similar to the Monarch Butterflies of our own world. If they went with Monarchs as the inspiration, Hawaiian Monarchs are known to have low amounts of toxins in them, possibly changing Butterfree into a Poison/Bug!
The possibilities for this Pokémon are fascinating!