This subject cropped up on another thread so I thought I'd post the details here for future searchers to find.
Green brake pipes, green brake lines, copper brake lines, nickel brake lines.
Whilst not necessarily aesthetically correct, I like to use the green coated brake pipes from 1980s cars.
I buy the longest length, part number A1234208828/64, and cut to length, bend with a hand-held pipe bender and flare with a flaring tool.
Only the purists will object to the incorrect finish!