Direct sun from noon to 2-3pm is "full sun" IMO.

usually.. anything over 6 to 8 hours is considered full sun ...

other than that.. buy and try whatever pleases you .. some will prosper.. some will fail .... that is the definition of gardening...

just build the bed out of the shadow of the house ... or plant shade plants in the part that gets little direct sun on the north side ....

ken

I have a mix of sun and shade plants at the NE corner of my house. Personally, I go by what the soil is like. If it is moist most of the time go for plants that like that. If it is dry during the summer, use plants for that. My corner is dry during the summer so I have plants that like that there.
Do not plant full sun tall plants though. They will flop over.
Remy

I worry that hydrangeas would not be happy there - always heard that morning sun/afternoon shade is best for them. Mine do great with only morning sun. Of course, summers are rather hot and dry here so YMMV. Good luck!

I would go with partial shade plants instead of full sun.

In terms of whites (or greens and evergreens) I'll share what I have that works on the shady north side of my house, in zone 5:

Annabelle Hydrangeas -- they perform beautifully, mostly shade.
White variegated hostas, of course
white Bleeding Hearts
Astilbe might do well provided you have ample moisture,

In terms of other shrubs, Fothergilla Major "Mt Airy" (white blooms)

I tried a white blooming Rhododendron in my shade area, and it never bloomed. They like more sun than I had originally thought, but this might work for you in the sunnier areas.

Whites add brightness to darker corners of the house, but I wonder if the dark purples or blues might "disappear" into the landscaping. But if you used the white as a backdrop to the other colors, I envision that would be a pretty planting combo.

Have fun with your garden plans.

I think you would be fine with hydrangeas there. If salvias are too floppy, try some veronicas or agastaches. You might even be able to grow baptista (false indigo).

I have a similar exposure in my zone 5 Iowa yard. Trees along one side, and then it slopes too, so it is a bit of an odd long bed. It used to be grass and mostly invasive Asian honesuckle shrubs.

I have only been gardening at this house for 1 1/2 years, so I am still experimenting; plus I am new to this zone and previously lived in zone 9.

I first considered this area part shade and planted accordingly. Now I see there are pockets of more and less sun. In this area the plants doing best are:

Hostas--This surprised me, but I see them in full sun around town now that I have started looking. Not sure if it is the same for zone 6.
Foam flower--this looks GREAT right now with tidy foliage and is still blooming. I had some red tulips behind the foam flower and they looked lovely.
Columbines--flowering nicely with airy foliage.
Agastache--the one I have has short white flowers, but blues are common I think. Overwintered and re-sowed abundantly. My soil drains well so may be why they like it there.
Garden phlox--were small plants last year from Bluestone spring sale. SO far they are growing nicely but will see if they flop. Today the whole area seemed to be in so much sun!
Daylillies--will see how they do this year
Foxglove--sowed last summer, getting ready to bloom, seems to be good for them in this spot.
Monarda, bloomed last summer and no flopping.
Soloman's seal--in a shadier pocket, but still gets some afternoon sun. Doing really well right now.
helleborus--one little helleborus which has been doing great so far this spring, to my surprise. When I realized how sunny the spot was, I thought I'd move this little plant, but it is doign well.
Toad lily--these are growing nicely and had attractive late flowers last year.
Lobelia--there are some nice blue lobelias available.
low growing veronicas--doing very well and blooming profusely.

Happy planting. :)

There are some white hydrangeas that bloom in full sun.

I came across a website for a Canadian gardener who plants Annabelle in full sun, and they're stunning.

I also have hostas in full sun. Just make sure you plant them and allow them time to establish before the peak of heat in the summer. Variegated forms are known to handle the sun more than others, but there are also some non variegated that work too. I have Gold Standard in full sun, Patriot, and a smaller non variegated tiara type, and hosta plantaginea and they've all done well for me.