What is the green heart event for Muffy in Harvest Moon DS?

There is no Green Heart Event. The event occurs at Yellow. You'll exit your house between 6am and noon on a sunny day and her Yellow Heart Event will begin. Hope this was helpful.

The event: Yellow Heart Event

» Exit your farmhouse

» 9:00 am to 12:00 pm, Summer season, sunny day Muffy will greet you as you leave your house. Today's weather is good so she suggests the two of you go out somewhere, perhaps a d-a-t-e? Tell her you'll go out on a date and the two of you go out to the Goddess Pond. At the pond Muffy lets you know that this pretty pond is said to be sacred. She's glad to know that you feel the same about this spot. Muffy decides it's time to go to a new spot on your date. You'll visit Kai at his summer food booth and he notices you two appear to be on a date. Kai says it'll be his treat so you get some food. Once your meal is over you both return to your farm. It's the first time that Muffy's enjoyed a date with a boy. yes there is a green heart event but it wont wrong it will turn yellow if you have 60 havest sprites and it will work good luck!