What feature associated with the head pattern in a Yellow Belly might appear brighter or predisposed to merging early?

The lighter areas on the head and neck just behind the head

While the body coloration is the most dramatic indicator, the head pattern, or 'head stamp,' can also show subtle signs of the Yellow Belly influence. Hobbyists often look for whether the lighter areas situated on the head and neck, particularly in the nape area just behind where the dorsal pattern begins, seem unusually bright or show a predisposition to lightening up or merging sooner than expected for a standard animal. A perfectly expressed Yellow Belly might specifically feature a dramatically lightened nape area, signifying the gene's presence early in development, even if the overall head pattern modification is not as consistently dramatic as the body changes.