Well, my guess is blue because if you look in A LOT of his books, there is always blue, unlike red or green or yellow.
1991 :>
Theodor Seusse Geisel Theodor Seuss Geisel
Vanessa's favorite colour is red
Their favourite colour is blue.
Her fav colour is pink and purple
His favourite colour is blue =]
They have no favorite colour.
his favorite colour is pink
His favorite color is blue.
His favorite colour was red
Adele's favrite colour is... blue!
Ernest Rutherford's favorite colour was green. Although he liked a lot of other colours too. His absolute favorite colour was green.