Answer: The percentage of each phenotype to be expressed is *50%* each
Explanation: In codominance, two alleles for a particular trait are equally expressed in an individual carrying it, neither an allele is dominant or recessive over the other. In this case the individual shows the two traits of the allels.
Furthermore, when 2 Christmas parrot are crossed with red and green color in an homozygous codominant trait the heterozygous F1 generation will either be red with traces of green or green showing traces of red.
If parrot 1 (Red) is represented as PR PR and parrot 2 (Green) is PG PG the cross between them will give PR PG therefore, the individual shows both traits.
