Answer:
See the answer below
Explanation:
Heterozygous plants will have the genotype Bb. Crossing two heterozygous plants;
          Bb   x   Bb
        BB   Bb   Bb   bb
Genotypes
BB - 1/4 or 25% (blue color)
Bb - 1/2 or 50% (blue color)
bb - 1/2 or 25% (purple color)
Phenotypes
Blue color - 3/5 or 75%
Purple color - 1/4 or 25%