Royal motifs of yellow castles on a red background and yellow fleurs-de-iris (three petaled iris) speak to the royal patronage. These motifs can be seen in the lower corners of this picture.
Yet these motifs also led to the importance of Christ's heritage, just as the rest of the window does. The link between the Old and New Testament seems to be one of heritage. This link is reminding the viewer of Christ's own royal heritage and the lineage of Mary.