COP v3.0:fitness-purpose; colour-differential

11.4 Colour Differential 

It is both the cladding manufacturer and the roof cladding contractor's responsibility to ensure that the same brands of pre-painted material are used on the same building.
Failure to do so could result in differences in colour, gloss and weathering, which quickly becomes obvious.
The differences come from different paint formulations and do not necessarily indicate that the materials will perform differently in service. All New Zealand manufacturers provide information about the manufacturer, the type of coating and the manufacturing date in the branding on the reverse side of uncoated and colour coated steel. Double-sided coatings are not branded.

11.4.1 Touch Up 

Air-drying touch-up paints have different weathering characteristics to the baked-on finish of pre-painted coating systems and variations in natural light conditions will emphasise these differences, producing an unacceptable aesthetic appearance.

Spray cans should not be used for repairing scratches on pre-painted sheeting.

If the scratch is obvious from 3 m, the sheeting should be replaced, if not then it should be left alone. Minor surface scratches become less noticeable as the coating weathers and are best left as they do not appreciably affect the corrosion inhibiting properties of the material.

Widespread damage caused by rough handling or an accident, however, should not be corrected by repainting, but the affected material should be replaced.