Pollen

Some of my colonies are bringing in  huge amounts of pollen right now, I'm sure they know what they are doing.  The picture is from a brood frame in one of those colonies.
The enormous variations of colours shows what a diverse range of plants the bees are foraging from.
The lightest is almost white to the darkest black, which is almost certainly poppy.
There is a colour chart in Wikipedia and although it is probably North American and incomplete for the UK, it does give a guide to what is coming in.