"It became our turn to pick a colour. But in fact, we had accumulated a lot of yellow material so we needed to use it. So that's why we had to wear yellow," he said.
Since the war started, many people have used the Ukrainian flag and its colours to show solidarity with the country.
The war has resulted in cancelled spacecraft launches and broken contracts.
Roscosmos chief Dmitry Rogozin has warned that the US would have to use "broomsticks" to fly into space after Russia said it would stop supplying rocket engines to US companies.
Many worry, however, that Rogozin is putting decades of a peaceful off-planet partnership at risk, most notably at the space station.
Nasa administrator Bill Nelson played down Rogozin's comments, telling The Associated Press: "That's just Dmitry Rogozin. He spouts off every now and then. But at the end of the day, he's worked with us."
"The other people that work in the Russian civilian space programme, they're professional," Nelson told the AP on Friday.
"They don't miss a beat with us, American astronauts and American mission control. Despite all of that, up in space, we can have a cooperation with our Russian friends, our colleagues."
Nasa astronaut Mark Vande Hei — who on Tuesday broke the US single spaceflight record of 340 days — is due to leave the space station with two Russians aboard a Soyuz capsule for a touchdown in Kazakhstan on March 30.
In April, another three Nasa and one Italian astronaut are set to blast off for the space station.
- AP