ios - Changing color of text on send button in disabled state on MFMailComposeViewController -

i want change send button text color when in disabled state.

here code -

if mfmailcomposeviewcontroller.cansendmail() {     let mail = mfmailcomposeviewcontroller()     mail.navigationbar.tintcolor = uicolor.red     mail.mailcomposedelegate = self     present(mail, animated: true) } else {     // show failure alert }