How to change UISearchBar Font Size & Color?

To change text and placeholder searchbar:

// SearchBar text
let textFieldInsideUISearchBar = searchBar.value(forKey: "searchField") as? UITextField
textFieldInsideUISearchBar?.textColor = UIColor.red
textFieldInsideUISearchBar?.font = textFieldInsideUISearchBar?.font?.withSize(12)

// SearchBar placeholder
let labelInsideUISearchBar = textFieldInsideUISearchBar!.value(forKey: "placeholderLabel") as? UILabel
labelInsideUISearchBar?.textColor = UIColor.red

Here's how you can change the font and text color on latest Swift:

let attributes = [NSAttributedString.Key.font: UIFont.boldSystemFont(15), NSAttributedString.Key.foregroundColor: UIColor.gray]
UITextField.appearance(whenContainedInInstancesOf: [UISearchBar.self]).defaultTextAttributes = attributes

In the iOS 13 or newest, the UISearchBar has a property called searchTextField. But earlier, we can not use this property.

So, we can extend for UISearchBar:

extension UISearchBar {
    var textField: UITextField? {
        if #available(iOS 13.0, *) {
            return self.searchTextField
        } else {
            // Fallback on earlier versions
            for view in (self.subviews[0]).subviews {
                if let textField = view as? UITextField {
                    return textField
                }
            }
        }
        return nil
    }
}

And use:

searchBar.textField?.font = UIFont.systemFont(ofSize: 12)