All 89 bee plants
Ribwort plantain pollen
Plantago lanceolata
Pale dull cream, faintly grey, in the cream / white range.
FloweringApril to October
PollenFair
NectarNone
SeasonSpring, Summer, Autumn
WhereWaste and verge, Farmland, Garden
It yields no nectar, so the bees take its dull pale pollen only as a makeweight.

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.