Three Russian astronauts were not making a political statement when they boarded the International Space Station in mid-March wearing yellow flight suits with blue highlights, the colors of the Ukrainian flag, according to a NASA astronaut who was on the station at the time to greet them.

“I think the folks that wore them had no idea that people would perceive that as having anything to do with Ukraine,” said the NASA astronaut, Mark Vande Hei, who returned to Earth last week. “I think they were kind of blindsided by it.”

During a news conference on Tuesday, Mr. Vande Hei said the colors were those of Bauman Moscow State Technical University, which all three of the new arrivals had attended.

Mr. Vande Hei and a Russian astronaut, Pyotr Dubrov, spent 355 days in orbit. They and another Russian astronaut landed in Kazakhstan after a short trip back to Earth in a Russian Soyuz capsule. While relations between the United States and Russia deteriorated on Earth’s surface after the Russian invasion of Ukraine, the two countries continued to cooperate as usual to safely bring the astronauts home.

The American astronaut said he had not paid attention to bellicose social media postings by Dmitry Rogozin, the head of the Russian space program who shared a video that suggested the Russians might strand Mr. Vande Hei on the space station.

“Quite honestly, I heard about the tweets from my wife,” Mr. Vande Hei said. “I never perceived those tweets as anything to take seriously. I just had too much confidence in our cooperation to date to take those tweets as anything but something that was meant for a different audience than myself.”

He said people on the station did talk about the Russian invasion of Ukraine. “It was not a topic I shied away from with my crewmates,” he said. “They weren’t very long discussions, but I did ask them how they’re feeling and sometimes ask pointed questions.”

Mr. Vande Hei also said that he trusted his Russian colleagues. “We supported each other throughout everything,” he said. “And I never had any concerns about my ability to continue working with them. Very good professionals, technically competent and wonderful human beings.”

Mr. Vande Hei’s 355 consecutive days in space set a record for the longest continuous stay in orbit by an American astronaut. Physically, he is still getting used to gravity again. “I’m still uncomfortable,” he said. “But humans are very adaptable. And I think that bodes well.”

Mentally, though, life is almost back to normal.

“I really thought that I was going to carry forth with this unique perspective of appreciation for all things novel about being on the planet,” Mr. Vande Hei said. “I’m a little disappointed with how normal it feels. I kind of wanted it to seem more strange being back.”