Contemplating flower colors
I’ve always wanted a cottage garden with a rose-covered arbor and now I have one. Never mind the roses are infested with Japanese beetles, I have a rose-covered arbor, a picket fence, and a whole bunch of flowers.
When I started my cottage garden, I decided on a color scheme that used blue and white flowers as background colors with shots of pink and yellow for accent colors. That was the plan.
Blue and white worked out well. True blues aren’t common, so many of my blues, such as Russian sage and cat mint, lean toward purple, but are close enough. Bachelor’s buttons are a good true blue—they’ve become a staple filler plant and have the advantage of reseeding themselves like mad. White is a color that’s easy to find as annuals at the nursery—mostly I use a lot of alyssum and baby’s breath with some white impatiens in a shadier area. For taller background plantings, I like Shasta daisies. Blue and white leave an overall impression of lots of bloom without getting in your face and every blue or white flower I’ve introduced has worked out.
Where I find I’m having issues is in the accent colors—pink and yellow.
There are pretty pinks and glaring Barbie pinks. This does not mean that all bright pinks are unattractive—I have some lovely bright pink dianthus and portulaca. But some flowers, such as the Wave petunias I unfortunately picked up this spring, are a pink so vivid it almost seems to have an internal glow. It’s a jarring unnatural color that just looks wrong in almost every context. I can’t quite define what makes a bright pink an acceptable bright pink and what is too bright and unnatural looking. I especially have trouble with this while I’m buying plants at the nursery. I do know I’m not buying pink Wave petunias again. Next year I’ll plant white petunias—can’t go wrong with white.
Yellow has also been problematical. I was aiming for a true, buttery, lemony yellow, but so often come up with a yellow that either leans heavily towards orange or is too bright. Like some pink flowers, some yellow flowers seem to almost glow with an internal light. Some manage to be both too orange and too bright. Marigolds are the worst—although there are some acceptable yellows in the marigold family, most marigold yellows are screaming, vibrating yellows that jump out at you.
Pinks and yellows in general aren’t the issue, it’s these particular pinks and yellows. I think what happened is that that plant breeders have produced flowers in the brightest possible shades to grab attention when they are in flats at the garden center. The trouble is that pretty pink petunias have a way of turning into garish pink petunias once they’re installed in the garden.
Interestingly, there’s also an electric blue lobelia that doesn’t offend my eye like electric pink petunias and electric yellow marigolds. I think this is because blue is a color that naturally recedes and doesn’t jump out at you like yellow or pink.
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Not sure of the variety. I tried to match pics from online photos and was surprised to find so many different shades of pink beebalm! I always think of it as being red.
It was supposed to be 2 pots of deep purple(! Grape bubblegum, I think it’s called, or similar) but one turned out to be pink. I’m happy with it. 
I've been meaning to reply to this post for a few weeks now, but have been too busy in the garden!
Purple, pink, and blue are my favorite color theme in my garden. Almost every time I try to branch out, I regret it because other colors seem to me to clash. I especially find oranges and true reds troublesome in my garden. Though I know some people find those combinations pleasing, and I've seen beautiful examples. Just not for me so much.
Sarah Raven has even helped me appreciate orange in combination with pinks and purples and the acid green-yellow of the Alchemilla mollis!
Though, again, not in my garden.
However, I do have a section for the hot colors, and I'm happy with them there. Just not near the cool ones.
I live near Winterthur Gardens, and Henry Francis duPont who created them, was passionate about a yellow/purple combo. I balk a bit at it in theory because, like you, I generally don't care for what I consider to be harsh or glaring colors, especially some yellows. And the softer yellow I prefer seems to be rare in flowers.
However, I do find in the early Spring I'm far more open-minded and find just about any color a welcome relief from the winter grays and browns.
So, even the forsythia doesn't offend too deeply. In fact, at Winterthur, the combination of the glaring yellow forsythia and pinkish-purple redbuds is stunning. The earlier-blooming combo of corylopsis and a pinkish-purple rhododendron is even more to my liking, with a softer, buttery, and to my eye not lemony, yellow.
I've put up a post at Houzz to illustrate, if you'd care to have a look, it's here. (You don't have to be a member to see the posts.)
How about this Phlox paniculata Thai Pink Jade?
Close up it's a light pink with darker pink centers that can read as soft pink.
Bright eyes is similar.
And I'm sure I've seen at least one or two other phlox. Also some verbena.
This Pentas might fill the bill: Sunstar® Pink Egyptian Star Flower
Oh, and a snapdragon or two, maybe?
Also, if a shrub would work, you have a pink Rose of Sharon or two. Pink Chiffon is one. And Sugar Tip has the added feature of variegated foliage.
Hard to think exactly what they were at the moment, but I'm sure I've seen lots of other soft pink flowers. Best of luck to you in your search.
Have you posted/can you post some pix of your garden?