What are the small green-colored leaf-like structures present outside the flower called?

The small green-colored leaf-like structures present outside the flower are called sepals. Sepals, along with petals and stamens, are collectively known as the perianth of a flower. The sepals typically form the outermost layer of the flower and serve to protect the flower bud before it blooms. They may be either separate or fused together and can be different in shape, size, and color from the petals.