There are many meaning under the flag " Happy New Zealand". Firstly, the use of sky blue can reflects New Zealand's pure environment and the great future.
Secondly, the use of black background colour symbolizes New Zealand's tough and steady national characteristics，Maori cultures and also the soul of our national ball - " Rugby".
Contrast the Black and Bule into flag's layout, which can fully representing New Zealand's development idea as protect the environment as well as keep the national features.
A white Sliver Fern can symbolizes sitting on the white cloud's New Zealand and also reprensents our beatiful country which possess blue sky and white clouds -- "New Zealand".
(I used the image of Sliver Fern in my design and which is from http://en.wikipedia.org/wiki/Cyathea_dealbata)
Credit for the fern goes to by Kyle Lockwood