Any question answered...

Strange as it sounds Sharpie could be the answer.

Emyr, not sure what you mean. The liners run pretty the entire length from shifter to mech. Obviously they are exposed where they run along the down tube. Purely for aesthetcs the white bugs me, as the rest of the bike has bike has very black parts.

Wrap the liner in black heatshrink where it's exposed? You'd have to be gentle shrinking it, but it should work.