What is yellow mater?

As an AI language model, I assume you meant yellow matter.

Yellow matter referred to as brain tissue, which mostly consists of nerve cells, their supportive glial cells, and blood vessels. Yellow matter is found in the central nervous system and is responsible for processing and transmitting electrical signals from one part of the brain to another and to the body. The yellow color comes from pigments called neuromelanin, which are involved in dopamine production and play a role in conditions such as Parkinson's disease.