For the sake of this poll, which color do prefer, the famous @Slewfoot tobacco brown or the wheat tan?
(I present this as a hypothetical because the Slewfoot brown fabric run is long over)
Photo credits to @NewYorkIslander and Voxsartoria
Browns were once pretty much a standard in wool suiting, along with blues and greys (and actually greens were more common too) in the UK and USA. Look at the old Apparel Arts illsutrations for a start. Brown and tan wool suiting is still not uncommon in continantal Europe - I have a very nice dark brown Pal Zileri lightweight wool suit. There were only really certain time periods, largely from the late 50s to 60s that brown became de trop in business suits, and then largely in Eastern metropolitan USA and the UK, and really only in the financial services industry. It's never been frowned upon in academia, for example. And even then you get brown suiting still throughout the 70s. It's arrant nonsense to suggest that these whole ranges of colours should be reserved for linen or cotton, much as like brown linen and cord too.
So fresco cloth is made in brown and tan colours for what reason? I would say that it is because there is still a market for them especially, as I said, in Europe, as well as amongst our fellow non-European iGents, who are in general anachronistic and unusual in the context of the wider population. BTW, if you search the archives of this forum, both Vox and Manton can be found in possession of brown or tan fresco and on record approving of it (although admittedly in Manton's case, not his first choice). I'm glad you think that my style history was accurate, though... I'd hate to have to stop teaching on the subject.
Whenever I've had a tan, beige or tan suit in the past, I've always found myself wishing I had a darker brown version instead - or as well - whatever the fabric (pace Foo).