Hey
I am not familiar with Kariva, but I can answer more about the green vs. blue pills.
The blue ones have the hormones, as you probably know. The green ones, again as you are aware of, are "sugar pills". These are placebo pills, meaning they essentially don't do anything for you, but they represent a daily pill. They're basically there for you to remember to always take your pill daily, and for some people, if they do not use the sugar pills, they often forget when to begin a pack, or sometimes get off track with timing.
Hope this helps!