So far I've been pairing them up with white mums and I think they look nice, but my girlfriend who is a florist and does this for a living says yellow mums or lilies would look great with them.
BTW, they are in my bamboo grove so there is A LOT of green. Lol
The pink mums go really well with the green ones !
I think pink flowers in general could be a nice touch of color to go with them since it's a japanese area and pink remind me of sakura petals.
I tend to like how purples and yellows look with them. I think purple would be nice here because it could match the hint of purple/blue in the wishing bamboo (I forget the real name of the item). Even a blue flower might be nice, if you use one that matches the colour of the flowers in the item on the bench (again I'm forgetting its name haha). In both instances though, I would switch the placement of the green mums with where there now are white mums.
I think mums go well with other mums or weeds mainly, though the fact that they're green means they're more flexible than purple/pink mums They're my favourite flower in this game though
I've been mixing a bunch of orange hybrids, mostly hyacinths, cosmos, pansies and roses, in with my green mums. I also added some bushes, weeds and white hyacinths and cosmos because they are two of my favorite types of flowers in this game.
I've planted them around my house with yellow and white mums and white cosmos. I have cedar trees planted and a few star fragments strewn among them. It looks pretty.
I personally pair them up with all other kinds of white flowers. I think white hyacinth and white cosmos are probably the best ones, but any white flower looks good with green mums and bamboo.
If you're a Packer fan go with yellow (Wisconsin FTW).
Or, if you're like me and not a sports fan, I think it looks really nice to have like a field of green mums with a pop of purple, pink, or red every once in a while, keeping the green dominant but making it more interesting.