It's usually 3: The black father, the red mother, and the blue son.
It looks cute if you plate it with the 黒文字 vertically like a pole (idea of KM26)
I think here it'd be nice to add some salt crystals to give a bit of a maritime flair.
Here I used 17 gr of 中餡, 20 gr for the coloured ball and about 3 gr for the gradation.
-