Yes, masses of pollen are visible to the naked eye, such as the collection found on the stamen of flowers like tulips. However, individual pollen grains are generally too small to be seen without magnification.
Pollen grains vary in size and shape depending on the plant species, but they are typically microscopic. While you can't discern the individual grains, a large accumulation of pollen, often appearing as a yellowish or greenish powder, is easily visible. This is what you see coating the anthers of flowers or dusting surfaces during allergy season.
Think of it this way: you can see a pile of sand, but you can't distinguish each individual grain of sand without a closer look. Similarly, pollen appears visible in its aggregated form, but its individual components remain too minute for unaided observation.
