Incomplete and Co dominance are somewhat confusing. The thing to remember is in Co dominence the traits don't mix. In incomplete dominence the traits do mix. Take a flower for instance. Say you have a red and a white flower that pollenate together. If flower color is Co dominant then you would get a flower with red and white pedals. If it is incomplete dominence then you would get a flower with pink pedals.

An experiment we could of done is exactly what I just talked about. Pollenate red and white flowers and see what color/s the pedals of the offspring are. We could do this with many types of flowers (roses, tulips, etc) and many different colors.