What is the value of a 1963 US 5 dollar bill with a green seal?

The green seal indicates your bill is a Federal Reserve Note. Despite the bill's age, circulated ones aren't considered scarce. They might retail for $6-8 in average condition.

If your bill is crisp and uncirculated it might retail for $15-18.

US Notes
Red-seal $5 US Notes were also printed in the 1963 series. Please see the Related Question for more.