I've worked with chemicals for 8 years, my entire professional life, and additionally I dye my own fabrics in clothing that I design and sew. A dye of some sort could be developed. What quantity of ivory do you currently need dyed, and which color?
If you are looking for a genetically-modified organism that is also possible, I would need to do some further research, but I have 6 years of experience cloning. However, my price is based on dying the ivory, not creating a genetically-modified ivory.