As a headset operator I always tell the flight deck if I see any kind of flame from an engine on start up and up to now this has always been acknowledged by the FD.With this the FD can reassure cabin crew if they report that passengers have reported seeing flames. If the flame continues for quite a few seconds I try to give a running commentary of what I am observing.The FD can then monitor the situation with the engine sensors and the information they receive from me and act accordingly. I've witnessed many a hotstart (look great in the dark) and the embreaer 145 on a cold morning provide a good display.However the best display I've seen was a BAE 146 when No. 2 engine disapeared in an orange flame which resulted in a return to stand for further inspection(no damage found).On the subsequent pushback when it came to restart No. 2 the FD asked me if they were clear to start the 'flame-thrower'.The people involved in engine starts that produce a flame know what the situation is unfortunatley the passengers don't and there lies the problem that caused this incident.