When “The X-Files” returns on Jan. 24, don’t expect one of those highfalutin’ reboots: The six new episodes are all about continuity — down to star Gillian Anderson’s signature hair color.

Back in 1993, when the Fox show first aired, Anderson dyed her blond hair red to play FBI Special Agent Dana Scully. This time, she opted for wigs.

“The first [wig] wasn’t quite the right red, so in some light it came off as strawberry,” she tells The Post. “The second wig was more the original color.”

The coherence goes deeper than hair color: Back also is David Duchovny as Fox Mulder, Scully’s colleague, confidant and, later, lover.

For Anderson — who also plays a witty society matron in the miniseries “War & Peace,” premiering Monday — there was a sense of unfinished business that not even the 2008 movie “The X-Files: I Want To Believe” resolved.

“I felt we needed another chapter,” the 47-year-old says. “I realized these new episodes could be a really fun thing for the fans, and potentially for us.”

Even before the era of social media obsessiveness, “The X-Files” had a passionate following. For Anderson, this was a challenge too.

“One of the concerns was whether we would be able to re-create exactly what it was,” she says. “Would we be able to give people what they enjoyed and was taken away from them?” she laughs. “These new episodes have that unique balance of story and cheesiness.”

If there was one through-line to the show, it had less to do with alien abductions than the bond between Mulder and Scully — and the actors playing them.

“There was the dynamic that had been written for us and the one between us,” Anderson recalls, possibly alluding to her often-stormy off-set relationship with Duchovny — though they’ve always denied rumors of their dating. “The writers were smart to keep [the characters’] relationship fluctuating. But the foundation is that they care about each other so much. They’re the love of each other’s life.”

From Scully’s mouth, fans.

Anderson, now a mother of three, didn’t easily slip back into a role she created when she was 24, and which earned her an Emmy and a Golden Globe. “When I first tried to connect with [Scully] again, I was reaching too far back into the past,” she says. “I had to allow her to be a grown-up version of herself, while tapping into her playfulness.”

Playful roles aren’t something the London-raised Chicago native has had many of — “[those] scripts don’t land on my desk,” she moans. Instead, she’s combined work in the sci-fi and thriller genres with dramatic period pieces like “Bleak House.” Her next venture’s both classic and contemporary: She’ll be at Brooklyn’s St. Ann’s Warehouse this spring playing Blanche DuBois in “A Streetcar Named Desire,” set in the present.

No mention of aliens, though. We can’t have everything.