Haas and Colsaerts both shot two-under-par 70s to head the leaderboard, with Louis Oosthuizen, Paul Lawrie and defending champion Lee Westwood just a stroke back.
Five other golfers were level-par after the first round, including former world number one Martin Kaymer and South African Charl Schwartzel.
On a cloudless, boiling hot day in the Pilanesberg, the 12-man field struggled in tough conditions, with a shifting breeze and the thickness of the rough causing much uncertainty.
Oosthuizen, the highest-ranked South African golfer in the world, claimed the early lead after he rebounded from a one-over-par outward nine, featuring three bogeys and two birdies, with a solid two-under 34 coming in, for a 71 overall.
But Haas, a Sun City rookie, stormed to four-under-par through 15 holes before slipping back to a 70 after dropped shots on the par-three 16th and par-four 18th holes.
Colsaerts, playing in the two-ball after Haas, produced the most consistent round of the day with just a single bogey, at the daunting par-four eighth hole.
The long-hitting Ryder Cup hero, also making his debut in the NGC, said it was hard work making allowance for the wind as well as altitude and the thickness of the semi-rough.
“The wind was a bit difficult to read. It always seemed to be coming off the side,” Colsaerts said.
“And with the effects of altitude and different grass to what we’re used to in the rough, it was very easy to get your yardage calculations wrong.”
The 30-year-old Colsaerts is one of the most entertaining golfers in the field, given his length off the tee, but he said he felt compelled to rein himself in because of the testing conditions.
“I didn’t use a very aggressive game plan, even with the driver when I used it. I think I played like everyone else, hitting the same spots, because you were better off hitting an iron from the fairway than a lob-wedge out of the kikuyu rough.
“I probably played close to my best in terms of management off the tee.”
Haas had the chance to separate himself from the rest of the field, but the American, whose father Jay is playing in the Champions Challenge on the same course, was satisfied with his round.
“I’d done well to get to four-under. There was a bit of breeze out there, the wind showed its teeth today, and, after missing a short putt on 16, I was happy to make a 10-footer for bogey on the last,” Haas said.
“I didn’t win it today, but I’m not out of it either.”
England’s Justin Rose, one of the pre-tournament favourites, will have to put pressure on the leaders from afar after he struggled to a one-over-par 73. The world number four birdied the two par-fives around the turn, but then picked up three successive bogeys from the 11th to 13th holes.