Three types of phenotype will be produced. One is grey, second is black and third is white.
The color is controlled by two alleles. Lets suppose B is dominant allel and b is recessive allele.
The black color organism has genotype BB and white bb.
The grey color is the indication of incomplete dominance and the genotype is Bb.
When two Bb will crossed:
Bb × Bb = 1/4 BB, 1/2 Bb , 1/4 bb.
So the 50 % chances are of grey organisms and 25 % of white and 25% of black.