An UIColor extension to gracefully adapt iOS 13 system colors: It returns the new system color if available, otherwise a color you specified. Supports Objective-C.

UIColor+iOS13Compatibility.swift

import UIKit

extension UIColor {

    @objc
    class func systemIndigo(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemIndigo
        } else {
            return substitute
        }
    }

    @objc
    class func systemGray2(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGray2
        } else {
            return substitute
        }
    }

    @objc
    class func systemGray3(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGray3
        } else {
            return substitute
        }
    }

    @objc
    class func systemGray4(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGray4
        } else {
            return substitute
        }
    }

    @objc
    class func systemGray5(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGray5
        } else {
            return substitute
        }
    }

    @objc
    class func systemGray6(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGray6
        } else {
            return substitute
        }
    }

    @objc
    class func label(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .label
        } else {
            return substitute
        }
    }

    @objc
    class func secondaryLabel(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .secondaryLabel
        } else {
            return substitute
        }
    }

    @objc
    class func tertiaryLabel(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .tertiaryLabel
        } else {
            return substitute
        }
    }

    @objc
    class func quaternaryLabel(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .quaternaryLabel
        } else {
            return substitute
        }
    }

    @objc
    class func link(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .link
        } else {
            return substitute
        }
    }

    @objc
    class func placeholderText(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .placeholderText
        } else {
            return substitute
        }
    }

    @objc
    class func separator(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .separator
        } else {
            return substitute
        }
    }

    @objc
    class func opaqueSeparator(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .opaqueSeparator
        } else {
            return substitute
        }
    }

    @objc
    class func systemBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemBackground
        } else {
            return substitute
        }
    }

    @objc
    class func secondarySystemBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .secondarySystemBackground
        } else {
            return substitute
        }
    }

    @objc
    class func tertiarySystemBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .tertiarySystemBackground
        } else {
            return substitute
        }
    }

    @objc
    class func systemGroupedBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemGroupedBackground
        } else {
            return substitute
        }
    }

    @objc
    class func secondarySystemGroupedBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .secondarySystemGroupedBackground
        } else {
            return substitute
        }
    }

    @objc
    class func tertiarySystemGroupedBackground(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .tertiarySystemGroupedBackground
        } else {
            return substitute
        }
    }

    @objc
    class func systemFill(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .systemFill
        } else {
            return substitute
        }
    }

    @objc
    class func secondarySystemFill(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .secondarySystemFill
        } else {
            return substitute
        }
    }

    @objc
    class func tertiarySystemFill(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .tertiarySystemFill
        } else {
            return substitute
        }
    }

    @objc
    class func quaternarySystemFill(or substitute: UIColor) -> UIColor {
        if #available(iOS 13, *) {
            return .quaternarySystemFill
        } else {
            return substitute
        }
    }
}