All pollen grains develop initially in groups of four called tetrads. I haven't found a database image to check yet, but the tetrahedral form of the above willowherb pollen suggests this species is one where the tetrad doesn't separate. The willowherb species below has separate pollen grains. The same pollen under darkfield illumination. The pollen did look a blue green when collected.
Pollen grains present a variety of challenges to study and interpret under the microscope.
Most pollen requires at least a 10X if not up to a 40X objective and higher to study both the gross structure and fine details. The shallow depth of field at higher magnifications requires constant refocussing and examining of grains in different orientations to build up a mental picture of the pollen grain's shape and structure. The yellow iris pollen below demonstrates this. This pollen was washed and hydrated and has swelled when compared with the untreated iris pollen in the title image. The outer coat of a pollen grain is called the exine and often shows fine structure.