Answer:
Codominance
Step-by-step explanation:
Codominance is the condition in which both the alleles of a trait are dominant and are equally expressed when comes together in the offspring. For example in ABO blood grouping in humans A and B allele are dominant so when they both come together in an offspring then they produce AB blood group in that offspring.
Here when true-breeding strains of salamander having yellow and red stripes are crossed together they produce offsprings having both yellow and red stripes that shows that the traits are codominant.
Therefore the pattern of codominance is most consistent with this observation.