My quick guess is that it is so dim, that our eyes are seeing it mostly with the rods (instead of the cones), which only see black and white. „In the night all cats are gray“

It depends on how bright it is where you are.

When it’s very very dim your color sensing part of your eyes, which are less sensitive to light, don’t work. Only the black and white parts of your vision work.

Kind of.

Uhhhh, I saw them yesterday in northen* hemisphere in Europe and they waren’t white at all… So my guess would be that it depends from where you look at it ?

But in reality they are more dull than on pictures, because photographers use Long Exposure to make the color brighter than they actually appear.

Edit: Typo

In my experience the aurora borealis is always green. I live in the north of Sweden.

Because it’s travelling backwards in time. That’s why it appears in black and white. You’re only seeing the past version of it.

Do you live in a predominantly white neighborhood?

Rods are more sensitive to light than cones. This is why in low light, colors appear muted. In this context, photographers can adjust the length of exposure to get an image that is more colorful than what our eyes can perceive. Really depends on how bright the aurorae are which can be affected by various factors such as light pollution, solar wind speed, and latitude.

It’s the green parts that look white / grey. I believe it’s more of an illusions - if you have something to contrast it with, such as the moon, you can start to see a slight green tint. The pink I saw last night was very noticeable though.

I live too far south to see it but my understanding is that at different layers of the atmosphere, the stellar material interacts with different elements. So, it gets green or pink or whatever depending on how deep it goes.

Wait, that’s what that white thing was? I thought that was a cloud.