Answer: none
Step-by-step explanation:
If we have that the color characteristic is regulated by the dominant gene R, by crossing two blue flowers with the recessive gene r, no violet flower will be obtained, since the rule of incomplete dominance describes that phenotypes can be obtained intermediates of homozygous parents, however in the case, we only have 2 parents with the same recessive conditions, which do not contribute to generate the violet, to produce one of the parents should have a gene that expresses the color red