If it was water, surely it would be smoking all the time, it's only doing it under hard acceleration. I'm not sure what colour as i was running in a bracket but someone i know suggested it was oil smoke.

69 Dart GTS 440 mopar .590 cam, Edelbrock heads, 3200#
best et 6.45, 106.78, 10.14, 132.88 mph, 1.47 60ft
best 60ft 1.36