An simple extension to NSColor to create a color from a six character RGB string. Written in Swift.

NSColor+RGB

// Swift 2.2

extension NSColor {
    
    convenience init(rgb: String) {
        
        guard rgb.characters.count == 6 else { fatalError("Invalid rgb value: \(rgb)") }
        
        let scanner = NSScanner(string: rgb)
        var hexValue: UInt32 = 0
        
        guard scanner.scanHexInt(&hexValue) else { fatalError("Scan hex \(rgb) error") }
        
        self.init(
            red:    CGFloat((hexValue & 0xFF0000) >> 0x10)    / 255.0,
            green:  CGFloat((hexValue & 0x00FF00) >> 0x01)    / 255.0,
            blue:   CGFloat((hexValue & 0x0000FF) >> 0x00)    / 255.0,
            alpha:  1.0
        )
    }
    
}

I believe that scanHextInt is now deprecated. And perhaps fatalError is a little brutal.

A more up to date implementation (Swift 5.8) might be as below. This is an extension on String, which I find more convenient.

var colorFromHexRGB: NSColor? {
    let scanner = Scanner(string: self)
    guard let hexValue = scanner.scanInt32(representation: .hexadecimal) else { return nil }
    let r = CGFloat((hexValue & 0xff0000) >> 16) / 255.0
    let g = CGFloat((hexValue & 0x00ff00) >> 8) / 255.0
    let b = CGFloat((hexValue & 0x0000ff) >> 0) / 255.0
    return NSColor.init(calibratedRed: r, green: g, blue: b, alpha: 1)
}