What happens to Superman if he goes near a red sun in space?

[DochaDocha]

What happens if Superman is on a space adventure and he runs into a red sun? Does he soak up yellow sun energy so he has enough to get away or would his superpowers disappear and he would die? Is he just really, really careful about where he goes in space?

Well, things like this have happened a few times throughout the run.

One of the more recent examples I can think of is Infinite Crisis, when he actually flew through a red sun, and he ended up losing his powers for an extended period of time (a year, I think; shortly afterward I took a break from reading comics out of boredom with the line). There was another Pre-52, Post-Crisis story in which he traveled back in time to Krypton, I think, and his powers slowly dissipated. There was another Pre-Crisis story in which his powers slowly dissipated when he was close to a red sun. I also recall an Animated Series episode in which the sun changed colors, and his powers faded. This type of interpretation is what I prefer; red sunlight isn't an "on/off" switch of his powers, but it's more like being exposed to that sunlight is akin to yanking the charger out of your cell or laptop, and all remaining "charge" is what was already stored and will be used up unless you recharge, in Supes' case going under yellow sunlight.

There are various other stories, however, that portray that if Superman is under red sunlight, his powers shut down immediately. I reject that premise, as I think it's kind of a lazy way to get rid of his powers immediately without resorting to Kryptonite. "Red Son" is a fantastic story, but it does this.

[Johnny Thunders!]

I think he loses his powers slowly, invulnerability is the last to go in All star Superman and in the silver age return to krypton.

[Dr. Jan Itor]

What happens if Superman is on a space adventure and he runs into a red sun?

Whatever the writer decides to happen.

[Joe Acro]

I definitely feel like he'd be in trouble. Admittedly, Supes doesn't often go into space without knowing where he's going, so I doubt he'd have a problem like this. If he did, though, he'd need to get away. It wouldn't take away his powers instantaneously, but he would experience difficulties. He'd eventually die if he had nowhere to go.

[dancj]

It's not about looking red. It's about electromagnetic wavelengths. Redshift means a shift towards the red end of the spectrum; it literally is red light.

If the sun was hurtling away from Superman at high speed then it is literally read light. If Superman is hurtling away from the sun then it'll just look red from his perspective.

Either way though - as adkal pointed out, it's still not coming from a red sun so there's no reason to expect it to have the same effect as a red son