The tribute paint scheme was Hamlin's idea and approved by Joe Gibbs Racing and sponsor FedEx following Leffler's death Wednesday in an accident at a dirt track in New Jersey. He was 37.
"He was the reason FedEx came into the sport and it just made sense," Hamlin said. "We asked the sponsor if it was good and Joe Gibbs Racing found someone Saturday evening to get somebody here and get it done."
Hamlin finished 30th Sunday.
Leffler drove 19 Sprint Cup Series in 2005 with JGR as it launched the No. 11 as its third team, and FedEx Senior Vice President of Marketing Laurie Tucker hailed him as "an integral part of the formation of the No. 11 team."
J.J. Yeley drove the car for four races that season and Hamlin closed out the year behind the wheel for the final seven events. Hamlin has driven the car since and the No. 11 is currently a predominantly black paint scheme.
The car was rewrapped by the team Saturday night into the primarily white paint scheme used when Leffler drove the No. 11.
"We feel fortunate to have had (Leffler) as part of both our Nationwide Series program and of course in the Cup Series where he helped us launch the No. 11 team with FedEx," team owner Joe Gibbs said earlier this week. "NASCAR is unique in that it really is one large family and Jason was well liked by all that knew him. His loss will be felt across the entire sport."