Bee Catcher and Pollen Tracking
Marking bees is established practice normally reserved for the Queen enabling her to be easily spotted during colony inspections. For the pollen tracking field trial it is also useful to mark individual worker bees, both in and out of the hive, in order to track their behavioural patterns and characteristics. If a sufficient number of bees are marked it should be possible to track them to and from their nectar and pollen source.  

First, locate a bank of plants that are in bloom and attracting pollinating insects - there might be several different species of plant in bloom simultaneously so in this case use different marking colours for each plant species.

Now we have to identify and select honeybees distinct from other pollinators such as the larger and stubbier bumble bees and predators such as hairless hornets and wasps.

The next task is to trap the individual bee for marking.

For this, wait for the bee to settle and for it to unclip the fengel coupling that holds together its fore and hind wing sets - the bee's wings will fold and tuck up fitting within its abd0men profile enabling it to enter the flower to reach into the flower nectaries. As the bee does this it is momentarily unable to fly off.
The most direct method is to clasp the bee by the sides of its thorax (the centre part) between thumb and forefinger, quickly dabbing it with the coloured marker.

Alternatively, for the butterfingered, there are a number of designs of bee trapping available from bee equipment suppliers but it is easy and much more fun to design and construct your own trap:-
The marking medium is applied to the topside centre of the thorax, as a non-toxic paint dabbed on via a marker pen or nail varnish brush - nail varnish and quick drying enamel paints are suitable for worker bee marking (but not for the Queen). The bee's thorax comprises a number of elastically coupled plates and wing root sockets so avoid painting any of these areas and features of the thorax.

Once marked, allow a moment or two for the paint to dry and the newly marked bee to settle before releasing it. 
With a sufficient number of foraging worker bees marked, the observation then takes place at the Apiary, first by observing the bees returning to the individual hives with their pollen basket loads and then opening up selected hives to cross relate to the recent pollen storage activity in the hive with the marked bees. With some luck, color marked bees might be found entering the hive and, once having done so, completing their 'waggle' dance to inform their sisters of the direction and distance of the pollen source.