I had in my mind that the little Teleri who was fishing was of the shore-dwelling Elves, and therefore their robe colour would change to something a little more water-y, or turquoise. The other Teleri is of Thingol’s host and still waiting, so he has the original colour. And the Nandor and Avari which also (mostly) stem from the Teleri also have different shades of green, denoting their status as “forest” and “dark” Elves. See? I think way too much about those things!
Actual quote: Now Ossë followed after the host of Olwë, and when they were come to the Bay of Eldamar (which is Elvenhome) he called to them; and they knew his voice, and begged Ulmo to stay their voyage. And Ulmo granted their request, and at his bidding Ossë made fast the island and rooted it to the foundations of the sea.