Generate a random color with a seed string using Swift 3

RandomColorWithSeed (Swift 3)

import UIKit

func randomColor(seed: String) -> UIColor {
    
    var total: Int = 0
    for u in seed.unicodeScalars {
        total += Int(UInt32(u))
    }
    
    srand48(total * 200)
    let r = CGFloat(drand48())
    
    srand48(total)
    let g = CGFloat(drand48())
    
    srand48(total / 200)
    let b = CGFloat(drand48())
    
    return UIColor(red: r, green: g, blue: b, alpha: 1)
}


// Identical seeds will lead to identical colors
randomColor(seed: "ben")
randomColor(seed: "ben")

// Similarly, seeds with the same character values will lead to identical colors
randomColor(seed: "ben")
randomColor(seed: "neb")

// However, this works well enough for something like article titles
randomColor(seed: "iPhone 7: Jet Black vs. Black")
randomColor(seed: "Vesper, Adieu")
randomColor(seed: "Bloomberg’s Report on Apple Watch 2")
randomColor(seed: "Is Donald Trump Actually Trying to Win?")
randomColor(seed: "Uber to Begin Testing Self-Driving Cars in Pittsburgh")
randomColor(seed: "Apple and the Pistol Emoji")
randomColor(seed: "Jack Off")
randomColor(seed: "Headphone Jacks Are the New Floppy Drives")
randomColor(seed: "Brief Thoughts and Observations Regarding Today’s WWDC 2016 Keynote")
randomColor(seed: "App Store Subscription Uncertainty")

Why not use String.hash instead of sum of scalars? It will bring you more entropy and will solve your case for ben and neb.

Hashing is now randomly seeded per application instance, per https://forums.swift.org/t/psa-the-stdlib-now-uses-randomly-seeded-hash-values/10789. So using String.hash will produce different results per application run, which defeats the purpose of using a seed completely.

What I did to deal with the "neb" vs "ben" problem is add the position of the scalar to the seed.

...
        var seed: Int = 0
        var i = 1
        for u in self.unicodeScalars {
            seed += Int(UInt32(u)) + i // add the position so that "ben" and "neb" do not produce the same seed
            i += 1
        }
...