I won't post the details as there are several tables, but the general gist is:
In 1.19 dying an item would change the stats and add class restrictions. However a lot of players weren't happy with being forced to wear one colour for optimum results.
In 1.20 the dying process will become 3 step;
1) Create the item you want
2) Treat (re-synth) the item to gain the attriibutes you want (e.g. +Piety or + Mind)
3) Dye the treated item to the colour you want to wear
Note that you can only dye an item once. Though there are plans in 2.0 to be able to dye a single item multiple times
I am not sure if dyeing is a final process, i.e. once you dye an item it can't be treated to get bonus stats.
Edited, Nov 15th 2011 3:21am by Magnesium02