The closest I came to this was a few years ago in Goa, where at the hotel we booked in for a 'couples massage'. It was a very respectable hotel and I'd anticipated it would all be very safe and sanitised, probably over a towel or swimsuit.
When we arrived at the massage room, there were two couches laid out side by side and two very pretty Indian girls standing by to perform the massage. They told us to '***** please' and when I stopped hesitantly in my underwear they said 'yes everything please'. My wife and I lay down side by side on the separate couches and the masseuses covered each of our bare ***** with a small white towel. I had a great view as the girl working on my wife began to rub oil onto her naked body.
Now Em's skin is very pale and 'English rose', whereas the girl giving her the massage had very dark, nut-brown hands. Watching her work across Em's back and up and down the backs of her legs was extremely horny! Eventually, to my rising excitement, the masseuse folded back the towel to reveal Em's pale round as s and began to work the oil in. It appeared her hands were very strong!
The masseuse said 'now turn over please', and without a beat Em flipped onto her back, her gorgeous pale pink-tipped breasts fully exposed as the Indian girl continued to stroke and push her soft white flesh.
I was hardly aware that the girl working on me had also been hard at work, but now she also indicated that I should turn over onto my back. This was a bit of a problem, as my excitement at watching her colleague's attention to my wife's pale nude form was now extremely evident! With some embarrassment I turned onto my back. With great professionalism, my masseuse simply draped the towel over my obvious and rampant erection and continued to do her work - although I did notice that she shared a wry smile with her colleague. I also got some very sarcastic comments from my wife later on!
The thing that sticks in my mind most was seeing the beautiful contrast between Em's pale flesh and the masseuse's dark hands. I would REALLY love to repeat the experience, but this time have a male masseur working on Em!