Not that we know of for sure.
There are many so called signals/indicators, but in reality it is very easy to confuse most of them.
Vanillas often are seen wearing "lifestyle" indicators and most swingers unaware of any indicators at all.
We long ago stopped placing any faith in such things, although it becomes a topic of conversation when we see someone showing an sign.
"Wonder if she knows? Do you think it might be for real or just another unknown?"..
Should we ask and find out?
Common(mis)conception; anklet on the right ankle, thumb or toe ring.
Wedding ring on the right hand, (is custom in some countries)
Bracelet on the left ankle.
Simply you cannot know, unless the person/people are very open publicly with swinging and wearing blatant clothing or accessories.
Bands are used at some events, especially where both swingers and vanillas are at a risque type event.