How to set the title text color of UIButton?

You have to use func setTitleColor(_ color: UIColor?, for state: UIControl.State) the same way you set the actual title text. Docs

isbeauty.setTitleColor(UIColorFromRGB("F21B3F"), for: .normal)

Swift UI solution

Button(action: {}) {
            Text("Button")
        }.foregroundColor(Color(red: 1.0, green: 0.0, blue: 0.0))

Swift 3, Swift 4, Swift 5

to improve comments. This should work:

button.setTitleColor(.red, for: .normal)

Example in setting button title color

btnDone.setTitleColor(.black, for: .normal)

This is swift 5 compatible answer. If you want to use one of the built-in colours then you can simply use

button.setTitleColor(.red, for: .normal)

If you want some custom colours, then create an extension for a UIColor as below first.

import UIKit
extension UIColor {
    static var themeMoreButton = UIColor.init(red: 53/255, green: 150/255, blue: 36/255, alpha: 1)
}

Then use it for your button as below.

button.setTitleColor(UIColor.themeMoreButton, for: .normal)

Tip: You can use this method to store custom colours from rgba colour code and reuse it throughout your application.

func setTitleColor(_ color: UIColor?, 
               for state: UIControl.State)

Parameters:

color:
The color of the title to use for the specified state.

state:
The state that uses the specified color. The possible values are described in UIControl.State.

Sample:

let MyButton = UIButton()
MyButton.setTitle("Click Me..!", for: .normal)
MyButton.setTitleColor(.green, for: .normal)