红旗 carries strong revolutionary symbolism - the flag of the CCP and the PRC. It also names 红旗 (Hongqi), the state-owned luxury car brand founded in 1958, traditionally used for parade limos that ferry top leaders past 天安门 (Tiananmen) on October 1.
usage
Measure word for the flag itself is 面: 一面红旗. For the car, use 辆: 一辆红旗.