This article explains how self-tanners that contain certain three ingredients WILL turn you orange.
Apparently, the main ingredient in self-tanners is DHA (Dihydroxyacetone), which reacts with protein to enhance colour. DHA is pH sensitive -- the pH level is what determines whether your skin will be brown or orange. For a nice colour, the pH level needs to be between 3 and 6. Anything higher than that means o.r.a.n.g.e.
There are three ingredients present in most Self-tanners that have a very high pH, more than 6.
These are: Stearic Acid, Triethanolamine, and Mineral Oil. When these are in a self-tanner, they raise the pH level to "orange levels".
So, if you don't want to look orange, avoid any self-tanner with these ingredients !
I'm also thinking about preparing the skin with something acidic, like lemon juice... I'll get back to you with this after I've done some experiments on myself.