>>31015404The red makes it stand out from Aipom, and it emphasizes the hands on its tails as the most eyecatching, as well as most important, feature in the design.
Aipom's fingers are divided into two parts: normal digits and the circular end digit. Ambipom's fingers are realistically shaped, but still keeps this divide in place.
Fingers are rosier toward the end, and making Ambipom's fingers reflect this adds to their more realistic nature.