I don’t know if that’s true. There are so many variables to consider and no one magic bullet.
@TOMTE made some very good points. Birds that are flightier are generally more predator savvy so a breed that is selected for instinct is important as well as color. Here are a couple threads well worth reading:
This on chicken camouflage through the eyes of a raptor:
https://www.backyardchickens.com/th...camouflage-for-free-ranging-chickens.1677023/
And this on extreme free-ranging:
https://www.backyardchickens.com/threads/landrace-adaptive-breeding-discussion.1624350/
Lots of good info in both. Your climate and vegetation plays an important role in which chickens are least visible. If you are letting a bunch of Buff Orpingtons run around in bare pasture they will be very obvious to predators whereas if your chickens are something more like Brown Leghorns in a thick undergrowth you will have fewer losses. Breeds that we often consider for our backyard flocks because they’re cute and fluffy are often not well-suited to free ranging because they have not been forced by natural pressures to adapt to their environment. I hope that helps. Sorry if it’s a little long-winded.