Anodising produces a layer of alumina (which is a very hard substance) on top of aluminum which greatly increases it's scratch resistence. If you start with pure aluminium, the alumina coating produces a silky silver/white colour. If you start with an aluminium alloy, the colour may end up a darker grey and may be patchy, especially over welds. To make it a pretty colour it's common to dye it such as those nice reds and blues seen on Goodridge brake hose fittings. As the coating is porous it's usual to seal it with a laquer or paint which will take to the coating very nicely.
To do a proper job the time and the electrical current used in the process have to be controlled which should be taken care of by any decent anodising company. Once anodised the finish may be what you want or you may find variations in colour, from there you can laquer or paint to get the match you need.
