To hell with being outdated.. be yourself and go for tan if you wish Pye End. Mine are cream and were worth the extra cost when buying new....everyone admires them.
Seriously, these sails are 30 years old. I've been told that the tan ones resist UV degradation better than white ones. Don't know if it's true, but we love 'em!
Our sails are almost chocolate brown, Kevlar and great when trimming in full sun, and we do a lot of that here in Oz.
Also as others have noted, easy to spot in a crowd, good UV resistance, will not show marks as much as white sails do, cooler shade than a white sail, less glare on deck, dries faster than a white sail.
If you think coloured sails are a bit dated have a look at the Sydney to Hobart race start on Boxing day, white sails are well outnumbered.
Far less dazzling on a really sunny day.Invisible at night.Ask sailmaker about uv resistant thread.
Actually tan fades if you don't put the sailcover on.
From what I read, square rigged sailing ships would often have sails of many different colours and patches. they were, of course, working vessles, so would use whatever cloth, in whatever colour, they could get hold of wherever they were.
They are traditionally associated with working boats, so to me look a bit odd on a modern yacht.
A nice variation is tan for the main and staysail, white for the jib and topsail
Before I bought my present white sailed beauty I looked at a Sadler 34 with bright pink sails. I don't know where it finally ended up - has anyone seen it? (must be difficult to miss!).