When Ri'Neref & his followers first moved to D'ni from Garternay, they installed a series of large fans to circulate air. This air came from a number of tunnels, sub-caverns, & other caves (possibly including the Carlsbad Caverns), some leading all the way to the Surface. Upon completion of the fans, a small group of workers disappeared. Many of the D'ni at the time, and afterward, believed that they made it to the Surface, and either couldn't return, or for some reason chose not to return. But the D'ni government held to the end that no D'ni had ever made it to the Surface. Otherwise, D'ni history makes it clear that the Tunnels & Shaft were the first attempt made at reaching the Surface.
Anna/Ti'ana raised Atrus in the Cleft, right next to the opening to the Shaft. If any other D'ni Survivors had come to the Surface, I'm sure Anna & Atrus would've stayed with them (or vice-versa), or we would at least have some kind of record of this event. As for the vanishing workers from Ri'Neref's days...
In one of Gehn's Journals from Riven, he spoke of the Amad, the Surface-dwelling people of his wife, Keta:
"The construction of the imagers has proceeded without fault. It is interesting to see how easily I've been able to adapt the D'ni technology to mimic that of the Amad; in some ways the similarities between the two cultures was striking. I wonder if perhaps there had been communication or commerce between the two cultures in earlier times; maybe Keta's people were even descendants of the D'ni. It pleases me to think so."
Surface-dwellers, around the turn of the 19th Century, in New Mexico, with
any kind of electrical technology (let alone imager technology) sounds positively absurd---unless there had been D'ni influence.
There are also several things in Native American culture from the region that could point to this. The name "Pueblo" was given to that tribe by the Spanish, but the Navajo people called them "Anasazi", meaning "ancient strangers" or "ancient aliens". Additionally, the Anasazi believed that their ancestors originally came from underground, through sacred openings to the underworld. Underground pits in Anasazi dwellings, called "Kivas" (afterwhich the 4 pits in Minkata are called), symbolized these openings.
And as discussed in the "Ancestral Pueblo and D'ni" thread in this Forum:
"Some modern Pueblo people in the Southwest still use the kiva as their holy chamber, and among those who speak the language of Tewa, the kiva is called te'i, 'the place of the cottonwood tree.' The kiva is thought to be a bridge between the underworld and the world above, and the hole traditionally placed in the kiva floor, just beyond the deflector stone and in front of the ladder, represents a place of emergence. In Tewa this hole is called p'okwi koji, 'the lake roof hole,' which leads up from a mysterious underground lake...."
This reference to a Tree is very interesting, and the reference to an underground lake is incredibly striking.
It's hard to say how far any Surface-dwelling D'ni could have traveled without much in the way of technology, but considering the D'ni Year 0 began on April 24, 7657 BC, their descendants could've traveled quite far. On the other side of the globe, "Uru" was a word in ancient Sumerian for "Deep City", and Sumerian legend tells of a great underground people.
Finally, in Dr. Watson's account of the rediscovery & early restoration of the D'ni Cavern, he said this about Elias Zandi:
"It was this meeting in the city where I realized that Elias and I differed on our views of the future of D’ni. It appeared to me that he was taking some rather extreme view regarding restoring the city to its 'original glory' and re-inhabiting it with people who called themselves D’ni. He said things like 'We feel the call, for many of us have the blood of D’ni within us, and it calls us home.' I must say that I understood some of what he was espousing, but not the extreme to which he was taking it."
The D'ni had no "official" or "sustained" contact with the Surface, so I would hardly say that they had any "colonies". But there is evidence that descendants of the early D'ni walk among us...
_________________
".rezuhnuh voohee tsahnril robotesh gelenij"
"The ending can never truly be written."