Green, yellow and black can make for a pretty ugly American flag, but these three colors play really well off each other in this section the garden. It started out as a Japanese area with no regard to color, but I soon took notice and quickly moved some plants around to enhance the continuity of this color scheme.
Hues ranging from bright yellow to dark green are represented, as is the year-round black provided by black mondo grass (Ophiopogon planiscapus 'Nigrescens'). One of my favorite Japanese maples, Acer palmatum 'Orange Dream', has reddish orange tips on its leaves but is mostly bright yellow. There is also a tiny bit brown and white in this area, but in the same way skyscrapers are prohibited within the city limits of Paris, red, pink, blue, purple and silver are not allowed (mostly).
Another great combo: The upright racemes of the Empress tree (Paulownia tomentosa) coupled with the slightly darker purple pendulous racemes of Chinese wisteria (Wisteria sinensis). Both plants bloom at the same time, just as their leaves are starting to emerge, their verticality connecting the sky with the earth.
An edible combo that grows incredibly well in our cool & wet springs: Peas, spinach & dill.
And finally, mixing the living with the non-living: Stones & Soleirolia soleirolii (Baby's tears)