Warts are small, flat or cauliflower-like bumps. The colour varies from light pink and yellow-grey to brown. They may be so small you can hardly see them or be as big as nickels.
Genital warts are not always easy to spot. So not seeing warts does not mean the person is not infected. People can be infected without them having obvious symptoms for months. And, with girls they can be inside the vagina, where they are hard to detect. So warts can easily be transmitted without you knowing it.
Most people who get infected notice this after a few weeks to eight months after unprotected sex. But it can also take years for warts to appear.