Three blue things making my heart sing this month:  

Forgetmenot (myosotis) - which carpets and spreads so obligingly. It was here when I arrived, and has now migrated to every pot on my terrace. I don't mind a bit. The most perfect of blues ...in my humble opinion.

Bluebell (Hyacinthoides non-scripta) - I THINK these are English ones (deep blue with white pollen) but if you think they're naughty spanish ones then do let me know and I'll yank them out (with sadness)

Pulmonaria 'Blue Ensign' Exquisite blue, low growing. Mottled leaves.  Need more.