part of the variability in the info on calla lilies might be a difference between the large white basic flower version and the smaller, colored ones. i would suggest that a call to your local nursery would settle the issue pretty quickly, rather than trying to get that clarified on the web
if we're talking about the same hibiscus plant -- classic red / pink / white family hibiscus, with the flowers that are about as big as your hand -- they need a lot of room because they can grow into pretty big bushes -- 6 - 8 feet tall and around, at least here in SoCal. definitely not candidates for those pots around the pond .
there are related plants with (relatively) small flowers, about an inch or so, that come in more colors including blues, but i've never grown them. again, a call to your nursery should be definitive.