What is the rarest type of Mew?

Could you elaborate on the topic of the rarest type of Mew? I'm fascinated to know which variant of this fabled creature stands out as the most elusive and sought-after. Is it a particular coloration, a unique trait, or perhaps a Mew that originates from a specific region? And how do enthusiasts and collectors go about acquiring such a rare Mew? I'm eager to understand the nuances and complexities surrounding this intriguing mystery.