What size is your current phone? What colour and model is it?
Ask yourself if you are happy with the size and go from there.
As for colour, they all look good to me. Silver is a known look, I think that you would have seen it around and it sounds like you like it. On the other hand, green is a bit of an unknown look, meaning that you are unlikely to have seen it in person just yet. It’s also possible that green could sell out fast as it’s the new colour and that usually proves to be the popular choice. So up to you if you want to go with the known colour or live a little on the edge and get the unknown, but potentially highly sought after colour. All speculation of course, I’m sitting back and just watching this year as I’m still happy with my XS Max in gold. I’m not normally a gold colour Apple purchaser, but it’s a pretty phone. If I was buying this year, I’d be tempted by the green.