We have not yet seen the book, but rumors tell us that the word “colourless” of the title not necessarily is a reference to Tazaki’s character, but to the fact that he has four friends with names that contain references to colors: 赤松、青海、白根、and 黒埜 (Akamatsu – red pine, Ōmi – blue sea, Shirone – lit.: white root, a plant name – Lycopus lucidus, and Kurono – black field), and who are usually referred to by their colors instead of by their full names.

But what to call them in ... Norwegian? Polish? French?
That is what life as a translator is all about. Luckily there is a lot of time to ponder the question.