Instead of brilliant red, the leaves persist in staying yellow. I would appreciate your thoughts on this matter. Variability of fall color may be based on cultivar, early fall weather conditions, and pH and nutritional levels of the soil. It is true that many of the ornamental pear trees have red to purple fall color, there can be fluctuations from year to year based on weather and moisture levels. How soon we have a frost, gradual temperature changes or extremely dry conditions can all alter fall color.
Some cultivars are more prone to color changes than others.
Test your soil to make sure your pH and nutritional levels are all in bounds, and then hope for the best. We have two Bradford pear trees and one Kwanzan cherry tree. These are three year old, beautiful, healthy, small trees. However, they have never bloomed. These plants need plenty of sunlight to bloom, so make sure shade is not a factor.