Carry a plant around the yard to see where it looks best with others. Repetition of color pulls the plants together. Partners in a plant marriage must have compatible light and soil requirements. Mauve and blue-gray harmonize with most colors. White goes with everything.
Bold reds look nice with pale blues.
Shades of gray, white and bluish-green are good for breaking up areas of green. Dark green foliage looks nice with silver. Bright gold and dark purple is very interesting. Place magenta colors with silver foliage. Pink and gray is a great combination.