Hi,
Let us get an introduction of the problem first, Incomplete dominance is a pattern of inheritance in which, offspring from the cross of two parents shows a phenotype that is not like either parent but in between both.
For example: Let us take the example of Oompah's hair that can be either red or purple or blue. As described in the question, Red is dominant so let us denote allele for Red hair with R. The other hair color is blue that is recessive, let us denote its allele with r. Now, there is another intermediate phenotype that is purple, let us denote it with Rr because it is derived through a combination of R and r.
Now, here is the key for all possible genotypes and phenotypes of Oompahs. There are only three possible genotypes and phenotypes for the hair color.
Genotype: Phenotype
RR : Red hair
Rr : purple hair
rr : Blue hair
This is because no allele can fully express itself over the other. So is we cross a red hair Oompah with Blue hair Oompah, let us see what will happen:
RR x rr
Gametes: r and R
rr: Rr : Rr : RR
It means that 25 % of the offspring will have red hair, 50% will have contain purple hair and 25 % will have blue hair.
RR: Red hair 25%
Rr: Purple hair 50 %
rr: Blue hair 25%
Hope it helps!
