Yes get to take an additional action card every time you develop on the colonist track.
This is incorrect. You get the additional action card when all of your columns have been developed to a particular row, e.g., when all your markers get to row two, you get an action card.
Matthew is correct. I played it wrong initially, where the colonist track always provided an additional action card, and the game doesn't work right this way. If you check the rules it's clear that you don't get the action card until you develop all of your columns to a particular row.