An Auckland resident is enraged a potential new flag flying alongside the current New Zealand one is the wrong shade of blue.
The flag is flying on the Auckland Harbour Bridge.
It is a lighter blue than the correct darker blue.
North Shore resident Rob Harpur said it was "totally unacceptable".
"It's not the flag they voted for in the referendum.
"If people are going to make a decision on the flag, they should be shown the correct one."
He predicted the supplier of the flag got the shade wrong but the New Zealand Transport Agency should have "picked up on it". He admitted the flag "bugged" him every time he looked at it.
"The bridge is the main public area where the two flags are shown together."
New Zealand flag consideration project communications manager Suzanne Stephenson said the alternative flag flying on the Auckland Harbour Bridge was made to the specifications developed with the designer, Kyle Lockwood.
Ms Stephenson said large flags, such as this one could give the illusion of "varying colours in different light levels".
She said it was typical for flags to appear to be slightly different colours because of the range of fabrics and printing techniques used.