In all of Hanuman temples, there would be one thing in common in his
idols. They are smeared with Sindhoora (Red Lead) and oil, a symbol of
life and strength. Does applying the Sindhoora has any reason behind?
Once when Sita was applying sindoora on the partying of hair on the
forehead, Hanuman asked her the reason for doing so. She replied that by
applying Sindoora, she ensured a long life for her husband. The more
sindoora she applied, the longer Rama's life would be. The devoted Hanuman
then smeared his entire body with Sindoora, in an effort to ensure Rama's
immortality. Hence Hanuman's idol is always daubed with sindoora.