A navy linen shirt can make you sweat more than a white cotton one. Most guys never find this out until they are standing outside in both, wondering why the “good” fabric isn’t helping. Linen breathes well. But a dark color still pulls in heat from the sun and that cancels out a chunk of what the fabric was doing for you. Nobody selling “linen is best for summer” mentions “Mens Summer Shirts: The Difference Between Looking Cool and Feeling Cool”