The image to the far left is a comparison of the Indian lotus as it appears from the ground and the darker mala is the same mala worn over a length of time - this change is due to the oils of ones skin as it permeates the seed.
The significance of the Lotus Flower: The lotus flower symbolizes spiritual knowledge and power. The lotus grows through the muddy waters, flowering above the surface into its beautiful form, and as the rains fall from above the drops don't stick on the petals but fall back into the water. Meaning that once someone has realization what falls into the world no longer affects them.
This conveys that a spiritual aspirant, while living in the world, should remain unaffected by the worldly attractions and should work towards spiritual unfoldment.