Black and white vs. coloured lo-fi testing

There's quite a trend I see for low fi prototypes to be made into a purposefully lower fidelity .

That is filters to switch everything to cartoony fonts, make lines look crayoned in, and, most commonly of all, everything is made black and white.

What is the value of testing a low-fi prototype in black and white as opposed to colour?

Obviously I can see the one that it takes away judgements on colour schemes. But does it actively take users attention away from visuals and gets them to focus on IA?

I guess it can have a big advantage for recognisable brands in that it avoids people saying "Ah, this is coca cola, I like/hate coca cola", but for unknown sites and apps this isn't a worry.

Just what reasons are there behind black and white prototypes becoming so popular? What are the pros and cons of black and white vs. colour in testing?