Paraffin also works for this purpose.
While you are fire breathing or other such impressive feats, put a small amount of paraffin on your hand (the back of your hand is easier) and light it. Unlike alcohol which burns with a blueish flame, paraffin burns with a bright yellow flame.
For further impressive ideas, if you tap the burning part of your hand (quickly!) - as if to pat the fire out - then you can carry some of the paraffin over to your other hand and make it look as if the fire is spreading.
It has been pointed out that, if you had a mouthful of paraffin at this point you could spray flame, using your hand as the ignitor.
I have not tried this and might result in harm... only to be tried near a handy hosepipe or swimming pool...