On a mid-day walk along Crissy Field I spent a little time birding in the wildlife protected area at Crissy Field where I spotted five Snowy Plovers (two of which were banded) The birds were quick to move up the beach to settle in little "pocket hollows" in the sand so I didn't get complete looks of their legs to see if they had double bands. The single bands that I did see were orange:blue on one bird and yellow:white on the other. (I hope this helps.)
I mostly spent my time there informing dog owners about the sensitivity of the area and the need to keep their dogs on a leash. With the exception of one all the owners were very willing to comply and showed appreciation for my efforts. I wanted to spend longer time their but I was more concerned about the possibility of my presence adding to the foot traffic so I happily moved along.