Throughout recent history how many cars are liveried after a works engine supplier though? I can't immediately think of any.
McLaren has had a silver-based theme during their Mercedes years, but they also had the Marlboro livery for the first two of those years. As far as I'm aware the current chrome livery is just an evolution of the old West livery. They may well be moving away from the chrome to distance themselves from the Mercedes days, but I don't think it was ever anything more than a coincidence or perhaps a symbolic nod once the West deal ended. I read that Mercedes themselves are expected to move to a more chrome look next year, which is perhaps the biggest clue that McLaren will change.
If they've no title sponsor then I guess it's likely to be white and red as a pointer towards Honda, but that may well change if a title sponsor is found.