What is the name of the flag that it hoisted up 5 minutes before the start of a yacht race?

Question

Sporties crosword Sunday Telegraph 30.09.07.

Answer 1

class flag

Answer 2

It varies, not all yacht racing rules are the same.  It is usually called "The warning flag" (5 minute mark, usually red or blue) or the "preparatory signal" (5 or 4 minute mark, usually red, blue, or black).

I hope that helps, good luck.