Randomly generate pastel UIColor in Swift

generateRandomPastelColor.swift

// Adapted from Stack Overflow answer by David Crow http://stackoverflow.com/a/43235
// Question: Algorithm to randomly generate an aesthetically-pleasing color palette by Brian Gianforcaro
// Method randomly generates a pastel color, and optionally mixes it with another color

import UIKit

func randomPastelColor(mixedWith mixColor: UIColor? = nil) -> UIColor {
    // Mix the color
    let mixColor: UIColor = mixColor ?? .lightGray
    var mixRed: CGFloat = 0, mixGreen: CGFloat = 0, mixBlue: CGFloat = 0;
    mixColor.getRed(&mixRed, green: &mixGreen, blue: &mixBlue, alpha: nil)
    // Randomly generate number in closure
    let randomColor: () -> CGFloat = { CGFloat(arc4random() % 256 ) / 256 }
    let red = (randomColor() + mixRed) / 2;
    let green = (randomColor() + mixGreen) / 2;
    let blue = (randomColor() + mixBlue) / 2;
    return UIColor(red: red, green: green, blue: blue, alpha: 1)
}