Comfrey, who knows one from t'other

I have a huge collection of plant photos, most of which I've never got round to labelling. I've never known which comfreys these are,

The blue one is about 2 foot tall and may be a hybrid, I've never had a seedling, it spreads by roots. That one flowers in summer

The white one is much shorter,about a foot, has black dots on some of the leaves (not a disease) and flowers very early, it's been out since new year but is always early. I've never had a seedling from this one either but it spreads well and makes a thick carpet