Anodising is used only with Aluminium, whereby you electro-chemically change the colour of the oxide layer that normally covers the metal. Over time, even this wears off though. There is a different process for stainless steel, but I cannot remember whether this is done in the melt or after the metal is rolled. It was black only, IIRC.

Renault do DIN size sleeve inserts for very little cash; I picked up a couple here second hand from a scrappy for about 50p (80 cents?). They fit into just about any DIN slot I have tried so far.

One of the few remaining Mk1 owners... #00015