Just left these behind in France - they were actually a much truer sky blue and absolutely stunning - wonderful scent too. My son has looked after my tray of delphinium seedlings (my own seed) and all 48 seem to be growing well - oh yes, I love blue too.
The best blue is always Meconopsis! No plant could be more heavenly blue. Sadly I've never managed to keep it alive long enough to flower...
I had one, it got infested with slugs and their eggs. It was gross.
Loads of Delphs, centaura, geranium, phlox, lobelia, clematis, campanula and (nearly blue) roses here. It is my favourite because, as stated, it matches everything.
Oh I forgot, erygnium 'big blue' too.
Ah! Penstemon 'heavenly Blues'!
I love blue flowers, although I don't fully agree that they really go with everything... in my "hot" border (everything from creamy white to yellow, orange, scarlet, maroon) I don't allow anythig blue.
But however... things I love: nepeta mussinii, borage (never quite IN a border, or it will take over, but I love to sow it or let it come up in places near or around blue things), bearded iris (in moderation... they leave such a sad hole after they are done), camassia quamash, bluebells (scilla), linum usitatissimum, various clematis and sages, miosotis (the tiny wild ones that grows wild all over the forest here), rosemary (especially the creeping one I planted at the top of a wall... I think it's called Point du Raz), variegated periwinkle, lesser periwinkle, hydrangeas. These are all tolerably true blues and really easy.
Not a true blue but bluish that I really love is Cerinthe major purpurascens (as an infiller betwen other plants). Not blue at all except in name (rather mauve and plummy purple) but gorgeous is the rose Blue Eyes (also look out for Pacific Dreams... it's somewhat less spctacular and not nearly as strongly scented, but a bit bluer).
New blues I'm trying this year, from seed, Lupinus arboreus and Verbena hastata "blue spires". Oh and th usual little lobelia, but I had never grown that from seed before.
Blues I wants (gollum, gollum!) some of the lovely blue geraniums.
Blues I don't like, Ceanothus, the lot of them. Can't say why!
Oh, I only had delphiniums once, in my old garden, will try again next year in the new one. And I hav some blue gladioli called Nori, but I haven't seen them blooming yet.
Oh, and Iìd love some of the "little-blue-ball" sort of eryngium... next year again