AAnyone have suggestions on how to do a two toned sweet 16 cake? Customer wants half white and half black on each tier... any suggestions. ...

You obviously don't have an airbrush, I have taped paper across a tiered cake before to airbrush a half and half cake.

Prior to having an airbrush I have painted half a tiered cake.  I have even done this for a half and half white and navy blue cake and it worked very well.  I used petal dust mixed with alcohol.

All the best.