No. The deadly webcap is an example of a poisonous mushroom that had brown gills. It can be found in northern Europe. Further, there is a broad category of diff

No. The deadly webcap is an example of a poisonous mushroom that had brown gills. It can be found in northern Europe. Further, there is a broad category of difficult to identify mushrooms referred to as "little brown mushrooms" that includes poisonous brown filled species. The notion that brown gilled mushrooms are safe whereas white gilled mushrooms are not sounds like region-specific folk knowledge, and given the way mushroom species migrate and the existence of relatively rare mushrooms, I wouldn't count on it to be reliable anywhere in the world. Positive identification is the only safe way to select edible mushrooms, and as this article points out even that bears the risk of false identification, particularly if you aren't fully aware of what other similar species to check for.