Yes the watermarks are from uneven distribution of surface waxes that causes the underlying anthocyanin colored cells beneath to have different shades. Think about adding candle wax over a basic clear color in different amounts and you have an idea as to how the colors can be affected. It adds a lot of distinction and beauty to those that exhibit these characteristics.
One of the sibs to 'Borscht' has the strongest contrast in the watermarks that I have seen and it seems to pass it on to its seedlings too.
Lynn is right about the clinic. All the semp crazies in one spot!
Kevin
