Yes. White polo shirts. BTW a new parent asked us (the PTA) if we would lobby to change this to a coloured shirt, after discussion between ourselves we said no (though the parent was free to take it up with the school instead).
Our reasoning was that though they might get stained etc more easily/quickly, because they are so cheap to begin with (£3 for 3 from Tescos) it was cheaper to replace the white ones more frequently.
Our school does have logoed polo shirts but because they are £8.95 EACH nobody buys them.