OK, I will weigh in with my BS.
From what I have found over the years of smoking awesome cigars is that there are two major variables in cigars.
1. Materials (the tobacco itself)
2. Construction
From my readings and my personal insight, I have found that that ash is very important.
The color does tell us about the content of the soil and the quality of the leaf used. A whiter ash usually (not always) conveys a higher quality leaf because it is not lacking in minerals needed to ensure good growth of the leaf.
The firmness of the ash can be used as a measure of construction quality of the cigar. A firm ash usually conveys that the cigar was packed properly and rolled properly. However, if the cigar is dry, it will be flaky despite how well it was built.
If the cigar is underpacked, the ash will be flaky, if the cigar is over packed, the draw will be tight and the ash will certainly be tight, too.
The color of the ash, btw, can also be impacted by the smoker. If you are power smoking your cigar (abusing it and not savoring it), it can lead to a darker ash as the leaf does not have time to burn completely through. I tried this as an experiment with a couple of friends. Don't power smoke. It also leads to throwing up. 🙂