Welcome Kathy!! I used several green 2-litre pop bottles for WSing last year. Actually, the container could be opaque, but the lid must be translucent so that the sun's rays can get to the seeds to promote germination. There is a thred on this forum about members' three tips for WSing which you could have a look at and of course read the FAQ and follow the link Wintersown.org. Good luck!!
Northerner.

Hi Kathy -

As Northerner said, it's the top that needs to be translucent; but as mentioned in the FAQ (I think) - the "rule of thumb" is to put your finger/thumb inside the container. If you can see your finger through the container, it's transparent enuf.

Have fun!