CGColor. :
let sp = CGColorSpace(name:CGColorSpace.genericRGBLinear)!
let comps : [CGFloat] = [0.121569, 0.129412, 0.156863, 1]
let c = CGColor(colorSpace: sp, components: comps)!
let sp2 = CGColorSpace(name:CGColorSpace.sRGB)!
let c2 = c.converted(to: sp2, intent: .relativeColorimetric, options: nil)!
let color = UIColor(cgColor: c2)
EDIT , . , Xcode FontAndColorThemes. sRGB, RGB.
, :
let sp = CGColorSpace(name:CGColorSpace.sRGB)!
let comps : [CGFloat] = [0.0, 0.456, 0.0, 1]
let c = CGColor(colorSpace: sp, components: comps)!
let v1 = UIView(frame:CGRect(x: 50, y: 50, width: 50, height: 50))
v1.backgroundColor = UIColor(cgColor:c)
self.view.addSubview(v1)
. , , :

, "eyedropper", , . , "eyedropper" Xcode iOS-. , sRGB.