Geranium Rozanne
Gentian Orya
Aconitum carmichaelii Arendii Group
Aconitum carmichaelii Arendsii Group
OK, so there is a touch of rose-making-the-blue-purple going on here too though I have weeded out the more obvious not-blues, but the theme, from palest to the boldest, with some blue-grey foliage too, is a cool blue palette. Fruit, leaf and flower all contribute and I refer you once again to Gertrude Jekyll. In fact I think I shall transcribe a little of it, to give you a taste! …well, for another time. I’ll Tweet and Instagram instead.
The Teddington Gardener 
Wow! You did it again! Such beautiful photos and the one color with so many nuances. Thank you.
That is very impressive for blue. Yellow is the easiest color to feature, but blue is the most difficult. It is the least common of floral colors. A bit of purple is just as acceptable as a bit or orange, white or brown is with yellow flowers.