The green metallic bee has a green head and will burrow into the ground. You will notice that when they return to their underground nest that their legs are loaded with bright yellow pollen that they have gathered for flowers in the area.
It's pollen grains
a pollen cell is yellow/orange
because of the pollen i dont know why the pollen is yellow
pollen grains are the yellow powdery in the anther.
Not all pollen is yellow.... Color in flowers is usually an attractant for insects (like bees) and birds to encourage them to pollinate the plant.