White Ash tends to have a lighter heartwood color, and wider spaced growth rings. By contrast, the heartwood color of Black Ash tends to be slightly darker, and the growth rings are typically much closer together.
The ash is always black after I take a bong hit and I dispose of the black ash. If I lit the bong 2 or 3 times, it would eventually turn white. So the difference for me between black and white ash is the level of incineration.