“Mad Men”

9 p.m. Sunday, AMC (10 p.m. beginning April 1)

Spoiler alert: “Mad Men” is looking brighter this year.

The dark wood browns and banquette burgundies have been traded in for mod white carpets and candy-apple red chairs.

Matthew Weiner, the “Mad Men” creator, producer, chief writer and guardian of secrets, has asked critics not to reveal even basic information about Sunday’s terrific two-hour season premiere. He would prefer you not know the year in which Season 5 is set, for starters. If that’s your idea of a spoiler too, consider yourself warned:

The year is 1966, and judging by the size of Don Draper’s sleek new apartment, the ad man (Jon Hamm, who also directed this episode) and his agency have avoided the financial disaster that loomed at the close of Season 4.

Draper’s new pad is not of the bachelor variety: The ladies’ man has made good on his marriage proposal to secretary Megan (Jessica Pare).

But it’s not just the Pop Art decor and Megan’s orange sherbet mini-dresses that lighten things up. When Don drops off the kids outside the suburban home of ex-wife Betty and her husband, he cracks, “Give Morticia and Lurch my love.”

That’s right: Don Draper tells a joke, and those usually brooding children actually seem (spoiler alert!) happy. The Summer of Love might be a year off, but good vibrations are loosening up the Draper clan.

Or maybe Don’s just glad to be rid of Betty, and who could blame him? The glum character and January Jones’ flat-lining portrayal were weak spots in the last two otherwise exemplary seasons. Her absence in the premiere is a relief.

Megan is Betty’s opposite. Chic, brunette, sexually provocative and at least somewhat independent-minded (she’s learning the advertising ropes from Elisabeth Moss’ increasingly assertive Peggy), Megan is blowing away the ’50s dust from Don’s life — and from “Mad Men.”

I don’t mean to present too rosy a picture. This is still a drama about people who can’t see the difference between truth and lies, or don’t care. Backstabbing, sexism and ambition haven’t gone out of style at Sterling Cooper Draper Pryce, and the Civil Rights protesters outside are little more than fodder for jokes (until they’re not).

As smitten with the free-spirited Megan as Don seems, he isn’t quite prepared for the changin’ times: A surprise party, complete with a few guests who might have wandered over from the Warhol Factory, leaves the birthday boy seriously unamused.

“What is wrong with you people?” Megan snaps at Peggy. “You’re all so cynical. You don’t smile, you smirk.”

Old ways die hard, even for a survivor like Joan (Christina Hendricks), the bombshell secretary and new mom who wants to get back to work as soon as possible.

When her disapproving mother suggests that a woman’s place is beside her man, Joan’s response probably says as much as we can expect to know of this season’s new-era “Mad Men.”

“And how did that work out for you?”