3-year-old and constipation

Okay, so I posted about my son urinating frequently.  I called the doctor and the nurse seemed to think that he may be constipated and that could be putting pressure on his bladder.  I agree with that, but now I have a new question.  She advised me to give him a children's laxative which I did.  His bowels moved about 4 hours later.  He went some, but not a lot.  My concern is that the poop was bright green TMI.  I mean really bright.  I thought back and he did eat green jello yesterday, but his poop has never been colored like this before.  Should I be concerned or is this normal?  I tried to Google green poop but didnt' get much help.

[3rdchild]

Call the pediatrician with an update and ask them about it.  
Just tell them you have a really crazy question...ha!  And then ask them....
(It was probably the jello)  Does he feel alright otherwise?