Looking at one of _Mike's earlier
pictures, it seemed that the watermark was applied to SS's by adding a little more blue. But using a SS from inside of the tree in Crystalsong Forest, I made a program in Java to check the RGB value of each Pixel, and found that where the watermark was applied, it changed ALL of the RBG values (253 or 254 instead of 255).
Watermark - Imgur (All from the Crystalsong Forest picture, Shadowmoon Valley not shown.)
Since I had trouble doing the same with an almost black SS from the Nether in Shadowmoon Valley, it seems to imply that the watermark is subtracting some of the RBG value, rather than adding any one color ontop. Does anyone know how the watermark is applied?