Aurora that looks grey is simply too feint for your eyes to perceive the colour[0][1]. One way you can confirm whether what you're seeing is aurora or not, is to take a picture with a digital camera. Camera sensors can discern the green (or whatever) hue, whereas the cones (which perceive colour) cannot pick up such dim light.
Once the aurora becomes stronger, you can absolutely see shockingly-vibrant green, pink, purple, and other colours, literally streaming/swirling/dancing across the sky. It's an unforgettable experience. I hope you have the chance to see this at full-strength sometime, and I absolutely recommend seeking it out if possible. (extra-recommended to watch while sitting in an outdoor hot tub at midnight in -10*C in Iceland, of course!)
Once the aurora becomes stronger, you can absolutely see shockingly-vibrant green, pink, purple, and other colours, literally streaming/swirling/dancing across the sky. It's an unforgettable experience. I hope you have the chance to see this at full-strength sometime, and I absolutely recommend seeking it out if possible. (extra-recommended to watch while sitting in an outdoor hot tub at midnight in -10*C in Iceland, of course!)
[0] https://www.neworld.com/blog/2018/aurora-borealis-and-our-ey...
[1] https://futurism.com/how-we-see-the-aurora-borealis-camera-v...