The Portugal international had a symbol shaved into the side of his head ahead of the Spanish side's 2-2 draw with Barcelona on Sunday.
Hairstylists Jose and Miguel Siero Leal, who are thought to be behind the new 'do, are quoted in Marca as saying: "He told us, as he had on many other occasions that he was looking for something different.
"We know him well and we had the idea of shaving a symbol that represents both peace and the calm a warrior experiences after battle. He agreed. His hair is very curly and you have to treat it carefully.
"He likes to wear it set or gelled. He knows that the television cameras follow his every move and he likes to look impeccable. Cristiano has a great personality and he's very ambitious. He's a winner. He only thinks of himself."
Ronaldo netted two goals in the highly-charged El Clasico at the weekend.