Is it safe to use swing-tops?

I have used swing tops in the past without issue. If you are worried about the seal you can buy replacement seals, which should probably be done every once in a while. I don't think it's necessary every time. I have bottled 2 batches using some Fischer bottles and had zero problems with the seal.

As far as the green bottles go. If you keep it out of the light you should have no problems. Beer Advocate has a good explanation as to why the green bottles will not be a problem.

Skunked beer: https://www.beeradvocate.com/archived-articles/527/

Fischer bottle: http://www.enveloop.com/wp-content/uploads/2008/09/fischer-beer-660-ml.jpg

I use old Grolsch bottles all the time, with no problems. I keep them in a box (out of the light) when priming, then they go into the fridge when ready, or the basement.

I get many re-uses out of the rubber gaskets, but do inspect them for cracks/tears that may prevent a proper seal.

I have a few cases of the swing top bottles in a 1 ltr size. I have been using them for years now without any issues. Every batch I make we use 1 of these bottles to store for at least a year and have had no problems when finally cracking one open.

I've bottled some of my beer in swing top bottles. I like them pretty well but they are difficult to scavenge (rare) and expensive to purchase. So if cost is your motivator buying a capper (check craigslist) and caps, and fishing bottles out of a local pub's dumpster (ask permission and wear gloves!) will probably be cheaper.

I had one seal fail on me, so you definitely want to get new seals from time to time. The beer in the failed seal bottle didn't skunk, it just simply didn't carbonate. I drank it anyway and it was fine, just flat.