When I visit various gardens I always pay attention to a combination of colors of plantings. I wonder as experienced gardeners create unity and balance of colors.
I have learned the color wheel and it was also very useful. Here are some examples of a wonderful combination of colors that you can see on the photos I had taken in Kensington garden, London.
In this garden there were shown various shades and intensities of colors. It's said red adds energy, yellow speaks of sunshine and friendliness. On the other hand, if one wants his/her garden to represent a cool place, so chooses blues, purples, pinks.
The eye is naturally drawn to a profusion of different shades. There in Kensington the gardeners showed that one can mix plantings with more intense colors. They combined dark red and green using variegated plants to bridge the two shades, or bright red with blue, or yellow with violet.
Once again, I payed attention to how white color was added as a lovely neutral. I often add silvery cineraria as a monochromatic color in rose beds. White is always a wonderful color to mix into any colored plants. However you might plant pinks, light reds, dark reds and maroons together.
Ultimately, your garden is a matter of personal taste.
I liked the advice 'Learn as much as you can and then feel free to experiment with a variety of plants. If something isn't working well in one place, you can always transplant it'.
If you're interested in what combination of color do I like best so this one: blue onions, violet veronica and green leaves (fifth photo).
Actually I rarely use color wheel, because if I plant perennials or bulbs in a combination of colors, maybe next spring some of plants won't survive. Years ago plantings with tulips and margaritas were unsuccessful.
Do you use color wheel when you plan something in your garden?