Red......................Green
frilled head/back.....frilled ears
red scales.............green scales
lava eyes..............emrald eyes
short neck.............long neck
long wingspand.......shorter wingspan
chaotic evil............lawful evil
fire breath.............acid breath
fire subtype...........air subtype
30 ft cone*...........20 ft cone*
*Those are based off wyrmling age. Red dragons breathe weapon are better an are 10ft longer than greens... but that range goes up 10ft per 3 age level..
So anyway, once I had the two columns down with what I wanted, I would get a coin and go down the list and flip the coin for each thing. Red will be heads, green tails... kinda like seeing which DNA strand is dominate.
Hope that helps.