設定標題顏色

//Swift
button.setTitleColor(color, forControlState: controlState)

//Objective-C
[button setTitleColor:(nullable UIColor *) forState:(UIControlState)];

將標題顏色設定為藍色

//Swift
button.setTitleColor(.blue, for: .normal)

//Objective-C
[button setTitleColor:[UIColor blueColor] forState:UIControlStateNormal]