There is nothing that you can put on Pink Ivory to prevent that beautiful pink coloring from turning into a dark golden brown with age and exposure to light and UV radiation.
My experience is that Pink Ivory is one of those species that does very well with nothing on it other than the bare wood that is polished throung 12,000Micro-Mesh, and given a coat of Renaissance wax as a temporary protection. The ultimate brown of the old pen is just as beautiful as the pink of the new pen.
Almost any finish will enhance the pink colloring when the surface of the wood is wetted. The difference is what happens later.
The finish that adds the least color to any new wood is wax, followed by a nitro-cellulose lacquer and Enduro.
The finish that has the least darkening of itself with time will be wax, CAB-Acrylic lacquer and Enduro. All other finishes will turn into an amber, or darker orange to brown color that will add to the changing color of the wood.
Since wax is the least durable, and Enduro is the most durable finish we can put on a pen (OK, I will accept the argument that Pexiglass or other acrylic materials are harder), it would follow that we should be using Enduro, if we want a finish on the Pink Ivory. Enduro also has a pretty good ability to block UC radiation.
There has been some discussion in the past about using ArmourAll to maintain the color. My experience is that it works if you like the feel of a greasy pen that looks as dead as the black plastic parts on my truck after it has aged and worn off.