The colour you choose for your aluminium joinery will depend ultimately on the look you are trying to achieve. For a modern, clean look you could opt for a tone a few shades up or down from your house cladding, match the joinery to the house cladding or contrast totally with dark or black joinery against a light coloured house.
Contrasting colours in natural tones will give your home a lasting quality that blends with the environment. When you are choosing your colour consider that different colours and finishes will perform differently in different environments. Lighter shades and matt finishes will perform best in the harsh Australian climate and can still maintain an up-to-the-minute appearance.