I don’t know much in terms of color management, that’s why I started with “I don"t know if it’s a correct way”.
I took the screenshot from the link posted by @pphoto (post #3), displayed in Chromium, and using the XFCE4 screenshot app. Imported in RT, I used the sRGB input profile.
I found the same color palette, with Lab values: https://d2r1vs3d9006ap.cloudfront.net/s3_images/1112392/CMYK_Lab_Skintone_inline.jpg?1414159126
