All 89 bee plants
Bell heather pollen
Erica cinerea
Pale dull lilac grey, in the grey range.
FloweringJuly to August
PollenFair
NectarYes
SeasonSummer
WhereMoor and heath
Moorland forage that runs ahead of the ling.

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.