I like to colour my works on the odd occasion, as you might have spotted. It’s pretty easy with titanium and stainless steel, and even easier when I start with a coloured object.
There are other ways though. One, from my good friend, Jill Hermans, is explained here;
and another, which involves some brand new technology, is explained here. Thanks to the ubiquitous TurboNerd for spotting that one.