Which sugar substitute should I use? 

Should you use the pink, yellow or blue?  Pink is saccharin.  It has the greatest amount of research behind it and has been in our food supply the longest.  Blue is aspartame.  It has lots of internet folklore about it, but no damaging research.  Yellow is the newest.  It is Splenda.  It has the least research behind it.  All of these train our taste buds to love the sweet taste.  None seem to be dangerous to our health.  However, the jury is still out.  Other options are Stevia, a natural sugar substitute or Agava Nectar- also good sweeteners. 

The safest recommendation-if you are going to use a sugar substitute, try Stevia or Agava.  If you don't like them, try to rotate the other three so that you minimize any unknown effect.  Honey can also be a nice alternative.