They have had the Wilson Duo in Yellow since the beginning.  Easy to find here in Midwest at pretty much any Wally World.  Personally, I love the Pinnacle Gold Yellow's at the price point around a buck a ball.  I use these to play to the green, and then use a softer touch ball for putting, like the Wilson 50 elite or Srixon AD 333.  I am a high handicapper just getting back into the game, but I thought this was common practice to always use a clean soft ball for putting.