The Long March 5's first launch used a LH2/LOX main engine with four RP-1/LOX Liquid Rocket Boosters (LRBs). Is this the first time that RP-1/LOX LRBs have been used in a successful launch to orbit?
above x2: Screenshots from the YouTube video shown below. Four RP-1/LOX LRBs emit bright white light while LH2/LOX main engine's exhaust is dimmer due to lack of thermal radiation from soot.
above: Long March-5 from Chinaspacereport.