The Urushi is a sap ... generally somewhat toxic. This sap is closely related to the sap from Poison Oak, and in fact you could actually use Poison Oak sap for a lacquer.
Lacquer is thinned with ethyl alcohol, rather than water, but you can use standard types of acrylic dyes to color it. The more dye you add, the longer it will take to properly cure and the softer the item would be, so less is better.... if you want the color darker or more pronounced, you simply add another layer!
The lacquer cures in the presence of heat and moisture ... most lacquer masters in japan refer to their lacquer workshop as their "bathroom" .... simply because the lacquer would cure best in that type of environment. Once cured, the lacquer is waterproof, hard, and non-toxic.... (well, it should be non-toxic in most cases, though the wet lacquer is toxic).
I'm going to have to see if Hobby Lobby carries any kind of Urushi lacquer... it seems to be something that would bring beauty not just in the present, but for many years to come ....