I'm not sure there are any hard and fast rules in regards to the latex color, personally. I think there is too much variation, or inconsistency if you will, in the latex, regardless of the color, to definitively say one has certain sound characteristics as compared to the others. Latex thickness, on the other hand, plays a huge role in the sound produced in a call, as does the reed cuts made in the primary sound reed.
The latex making process, which is primarily for medical purposes and such, is not exacting enough to produce the consistency in latex reed material for turkey calls to assure that any two calls, made exactly the same, will sound exactly the same. Anybody that has purchased a number of the same call from any manufacturer, or even those that make calls themselves, are very much aware that it is a crapshoot as to whether any two calls will make sounds of the same quality.
There are also variables completely unrelated to the latex color and thickness that play a role in sound quality of a call. The reed spacing, tension of each reed, the type of cuts put in the primary sound reed, the depth of the cuts, and the angles of the cuts all play a part in the sound created by the call. When you add the fact that each one of us has a little different shaped mouth, as well as different placement of the call in the mouth, and the ability to control air flow over the sound reeds,...it becomes clear that the color of the reed material is often a very insignificant factor in how a call will sound.
