All 89 bee plants
Phacelia pollen
Phacelia tanacetifolia
Deep navy blue, in the blue / purple range.
FloweringJune to September
PollenVery good
NectarYes
SeasonSummer, Autumn
WhereFarmland, Garden
A sown bee plant. The dark blue load is hard to mistake for anything else.

Easy to mistake for these
Closest pollen colours in our set, measured the same way the pollen identifier scores a match. Colour alone will not settle it, so check the flowering months and what is actually growing near your hives.
Out at about the same time
Saw a load like this going in?
Sample the colour against all 89 plants, then keep a forage record per hive.