The rules said that socks had to be white but some riders preferred to ride without socks, which technically didn't violate the rules. Still, some officials demanded socks, so there were riders who would use white paint on the area around their ankles. As a result, the rules were changed to, "socks, if worn, shall be white". However, even this got thrown out the door, after the UCI added mountain bike racing to it's jurisdiction, as in many regions it was impossible to keep them white, without buying a new pair for each race. The same problem had existed earlier, with cyclo-cross, but the CX crowd wasn't as vocal in its need for rule changes.