50 shades of gray

92-year-old Sumner plans group sex:

He may be 92 and feeble, but Sumner Redstone is still rarin’ to go in the bedroom, according to newly released recordings that portray the former Viacom and CBS chief as obsessed with threesomes — and even foursomes.

The XXX-rated conversations were made public Monday as Redstone’s ex-gal pal lost her bid to be reinstated as his health-care proxy.

In the series of raunchy recordings, Redstone was allegedly caught going into graphic detail about a threesome he had — as he tried to coax a female pal into a romp with him, another woman and a second man.

“This is your great lover. So I did what I said. Had a hot threesome,” says the man, identified as Redstone by the gossip Web site RadarOnline.

Redstone added that he was trying to arrange another ménage à

trois with a male buddy, “Bob,” according to Radar. The tapes were recorded within the past year or two, a source said.

“Bob’s never done a threesome with two men. He’s done it with three women. So he’s a little bit nervous, but he’s gonna come ’cause I want him to,” Redstone tells the woman, according to Radar.

“So what will probably happen will probably really excite you,” Redstone tells her and goes on to describe how he’ll choreograph the romp — sounding more like the director of a porno flick as he told her what each party would do to one another and in what order.

Redstone — the majority shareholder in Viacom and CBS who now can barely speak — allegedly takes a moment to chide the sexual performance of the woman he is calling.

Referring to the other woman he wants in the tryst, Redstone says, “She’s better than what you do,’’ according to the site. “She takes a long time, and she moans.”

It was reported earlier this year that Redstone has had women on $5,000-a-month retainers for sex. He was so active in the bedroom that he was warned by doctors to cut back, Vanity Fair reported.

Redstone’s lawyers did not return requests for comment.

The voicemail recordings surfaced as Los Angeles Superior Court Judge David Cowan dismissed the case by Redstone’s ex, Manuela Herzer, to reinstate herself as his health proxy.

Redstone booted her from the position and kicked her out of his Beverly Park house in October af- ter he discovered she was allegedly preventing other women, including his sex therapist, from seeing him.

Redstone also struck Herzer from his will, which had previously set aside around $70 million for her.

She contended he was incompetent at the time.

In a court deposition last week, Redstone called Herzer a “f- -king bitch” and said he wanted his daughter, Shari, to look after him.

“This testimony does, in fact, completely alter the case,” Cowan wrote in his ruling.

Herzer immediately filed a lawsuit against Shari Redstone and her dad’s staff, saying the daughter “embedded moles’’ in his mansion to create an “internal network of spies” to discredit her.