Answer
The whitish color of so-called white matter of the nervous system is due to the presence of myelin (myelinated axons).
Work Step by Step
White matter is found in subcortical brain tissues, in the in the outer regions of the spinal cord. Gray matter can be found in the cerebral cortex and in the so-called inner "H" shaped ( or butterfly shaped) gray matter formation of the spinal cord--cell bodies of interneurons, motor neurons, neuroglia etc Gray matter is usually composed of neuron bodies, dendrites, unmyelinated axons, and neuroglia.
