i went on the harvest moon ds web page, as i was stuck on this aswell and it said visit the blue bar between 3-5pm each day and eventually she will ask you what do you like in a girl and if you answer 'cheerful and pretty' she creates you a drink but it doesn't taste very nice, i tried this but my heart still isn't black though it may work for you so it's worth a try
There is no Orange Heart Event. Muffy only has a Black, Purple, Blue, and Yellow Heart Event.
3pm to 5pm
She comes to your house and asks you if you want to go for a walk with her. So really she asks you on a date. oyu go to the harvest goddes ppond first and then to the beach and Kai gives you guys food. for more information visit http://www.fogu.com/hm6/chan3/muffy.php?p= (this page is muffys page it has other stuff to) It tells you about lots of harvest moon ds stuff
Black heart event.
Are you making sure you are doing these two things? » Blue Bar » 3:00 pm to 5:00 pm ?
I believe she likes flowers, so give her a flower every day.
Muffy's Blue heart event is Blue Heart Event » Blue Bar » 6:00 pm to 8:00 pm, not Wednesday It may not work if you missed a heart event or you didn't follow those requirements.
Muffy's black heart event is at the Blue Bar from 3PM to 5PM. She pretty much asks you what type of girls you like. Answer, "Cheerful and pretty" and she'll be happy.
Give her wine (call up the supermarket on your phone and you can buy for 300g) everyday and her heart will go up quite quickly.
there is no green heart event.
A heart event in all harvest moon is a signal on how much a girl likes you
Walk from main path to Goddess Pond at 3:40 pm to 6:00 pm, not Monday