Herbaceous - Blue/Purple/Mauve

Choose on shape/arrangement of flowers:

Globular/heads
Tubular/Bells
Other Regular(ish)
Irregular

Arranged in rows - scroll down as required:

Compound flowers, globular heads or spikes

Regular flowers - (apparently) tubular or bell-shaped (may have flat top)

Regular flowers - flattish - ordered by petal number

Irregular (zygomorphic) flowers (not radially symmetric)

Note that some of the above spp. have white variants or may appear pinkish