Hello! I looked around for the answer to this for a while now, and I'm really hoping that this hasn't been addressed elsewhere, or else I'll feel dumb

I have become an avid Tamagotchi ebayer these days, and I have become almost obsessed with watching ebay auctions and hunting for deals on tamagotchi. I ordered a Japanese G1, (I know it's G1 because of the kutchipatchi sticker on the screen), and now I am looking for a G2. However, I do not know, how do you tell the difference between the two? I know that the American boxes have the purple/blue tops, and I know that the G1 has a Kutchipatchi sticker and the G2 has a hashizotchi sticker on the screen. But what do you do if you can't tell which tama is on the sticker, and it's still inside the Japanese box? Also, is there a guide somewhere that shows which color shells were released for which generation?
Thank you so much for your help! Again, I'm really sorry if this answer has been posted somewhere else. I looked around for an hour on the internet and I didn't see anything

But thank you so much!