Only if one of individual has incomplete dominance.
Explanation:
Using a Punnet square, only if one individual has incomplete dominance could have this ration. Otherwise, if the 2 individuals had a homozygous phenotype, whit one individual for dominant and the other for recessive, the ratio would be all purple.
I think it differs since the technology used before is kind of analog and the technology used now is kind of upgraded which has a higher storage capacity
