Thanks for your question. It is a good one.
Nd:YAG is the safest hair removal laser for darker skin types. There are other lasers that are more targeted and more efficient at removing hair, but in regards to preventing loss of skin color, the Nd:YAG would be better than these other two (Diode and Alexandrite lasers). You can feel confident that, if done well, the Nd:YAG will remove the hair and protect loss of your skin color, but make take one or two treatments more than the others.
IPLs can also be very good at removing hair, but be careful when it comes to loss of skin color in darker skin types. Your best bet is to go with a filtered IPL system that has an excellent track record with darker skin types. For instance, the Lux R handpiece on the Palomar Starlux 500 would be safe on darker skin types and does an excellent job at removing hair. You should be safe here.
As always, discuss these questions with your dermatologist prior to doing any hair removal procedure. Specifically ask about the laser and the potential for skin color loss.
Hope this helps!