As with other very dark rose seedlings, it is possible that this blotch will burn in full sunlight. Even so, the size and intensity of this seedling's blotch destine it to become an important parent for future generations.
Previous experience has shown that blotch size increases with maturity. Up until now, the Hulthemia seedling with the largest, most intense blotch has been M40-1. In the photos below it is easy to appreciate the change of the blotch as seen in the first immature bloom to that of the more mature plant grown outside.
Of note, the seedling at the top of this post, "O343", was the result of a cross made between two new seedlings from 2010. Using superior immature Hulthemia hybrid seedlings in crosses during their first year, has helped to shorten generation time and has produced some good results.