By NORMAN WINTER Move over, Red Abyssinian, there’s a new banana in town — the Siam Ruby, which has quickly found favor with tropical-plant nuts.Although I’m still a fan of the Red Abyssinian, it is just hard to pass up the colorful Siam Ruby. The trunk and leaves of this exotic tropical are burgundy with irregular iridescent lime-green variegation in the foliage.Its botanical name is Musa acuminata "Siam Ruby." There are scores of bananas that fall into that same genus and species.