Interesting, someone identified the new Seimei color as "parrot green":
(Below is Google translate from page linked in original tweet, has more detail than the separate English description)
Moegiiro is a yellow-green color that resembles a young leaf that sprout in early spring. It is a traditional color name that has been used since the Heian era, and is also separately described as "Moegi".
It is a color that symbolizes youth because of the color of the young green sapling, and was loved as a color for young people in the Heian period. In the Heike Monogatari, the 18-year-old Heike nobleman, "Atsumori Taira," wears Moe Ozori's armor, and the twenty-year-old master of the bow, "Yoichi Nasu," wears Moe Omoe's armor. Moe yellow is used as a symbol of young warriors, such as wearing.
It is also written as "Moegi Moegi". In this case, it refers to the dark green color derived from green onions and green onions, and became popular in the Edo period. By the way, the colors of Kabuki regular curtains are "black", "persimmon" and "moegiiro".