Also, there are more IP ranges that have been reserved for special use (there's an overview on https://en.wikipedia.org/wiki/Reserved_IP_addresses). I think it would be better to make 1 method that can return a pre-defined symbol of that range if the IP address is in that range. Otherwise, there would be an explosion in the number of IP addresses.
As far as I understand RFC4193 never defines its range being "private". There also are other private-ish address ranges e.g. fd00::/8. And what about v4-mapped v6 addresses? IPv6's situation is complicated (at least to me). I'd suggest OP to leave IPv6 situations untouched.