Elegant enum for custom colors worked on both iOS and macOS

ColorSet.swift

#if os(iOS)
    import UIKit
#elseif os(OSX)
    import AppKit
#endif

fileprivate struct ColorComponents {
    
    let first: CGFloat
    let second: CGFloat
    let third: CGFloat
    let alpha: CGFloat
    let model: ColorModel
    
    init(first: CGFloat, second: CGFloat, third: CGFloat, alpha: CGFloat = 1, colorModel: ColorModel = .rgb) {
        self.first = first
        self.second = second
        self.third = third
        self.alpha = alpha
        self.model = colorModel
    }
}

fileprivate enum ColorModel {
    case rgb, hsb
}

extension ColorComponents {
    
    static var red = ColorComponents(first: 255, second: 0, third: 0)
    static var green = ColorComponents(first: 0, second: 255, third: 0)
    static var blue = ColorComponents(first: 0, second: 0, third: 255)
}

enum ColorSet {
    
    #if os(iOS)
    typealias Color = UIColor
    #elseif os(OSX)
    typealias Color = NSColor
    #endif
    
    static let red = color(for: .red)
    static let green = color(for: .green)
    static let blue = color(for: .blue)
    
    // MARK: - Private
    
    private static func color(for components: ColorComponents) -> Color {
        switch components.model {
        case .rgb:
            let divider: CGFloat = 255
            return Color(red: components.first / divider,
                         green: components.second / divider,
                         blue: components.third / divider,
                         alpha: components.alpha)
        case .hsb:
            return Color(hue: components.first,
                         saturation: components.second,
                         brightness: components.third,
                         alpha: components.alpha)
        }
        
    }
}