Heat sinks and 'cooling fins'

A heat sink is object that absorbs and dissipates heat from another object using thermal contact (either direct - conduction transfer or radiant - the heat sink being dark and of rough texture to absorb radiant heat readily).

Heat sinks are important in electronic systems as there is always a heating effect of electrical circuitry. The fins are often found at the back of the device and also include vent holes to allow warm air to escape from inside the machine.

'Cooling fins' are projections that increase the surface area from which heat can be radiated away from a device. The fins project outwards making the area for emitting heat back into, say, an electronic circuit's container, smaller than the area emitting heat to the outside enviroment. This means that the heat energy is efficiently transferred outside the device's housing. Fins are found on a motorbike engine. They have a very large surface area to let heat out to the surroundings as quickly as possible.

You will find cooling fins on most appliances. Here is one on the back of a Hi-Fi unit.

What would be the best colour  and texture for the fins? .... and what would be the best material for them to be made of?

What other factors affect the choice of material and colour? (Think of design and price!)