I took the above photograph because this set of cremains was by far the most unique and beautiful ashes I have seen. So, I can say no to the question above. Not all cremation ash looks the same.
Cremation, where intense heat is used, has more variation in texture and color. They aren't "ashes" so much as calcified bone fragments and small amounts of salts and minerals. The unexpected colors range from iron (green) to copper (pink).
There is also Alkaline Hydrolysis, "water cremation." I can see and feel the difference in these "ashes". The color and consistency are similar to baby powder. I rarely see any variations.
Whichever form of cremation is chosen, I am able to create memorial jewelry from either.