Our endocrine system reacts a certain way to a colour because of the neurotransmitters we inherited from our parents. Here is how colour plays a role in our hormonal secretions. We see the colour if registers in our brain and our brain sends out a chemical messenger (a neurotransmitter) for a certain hormonal response from the appropriate endocrine gland. An Endocrine Gland (A ductless gland) manufactures one or more hormones and secretes them directly into the blood stream. They have a powerful influence on health and well-being. In fact, these minute secretions are produced all along the central body meridian by internal organs and glands which are a part of the body's endocrine system.
The endocrine glands include:
Pituitary
Thyroid
Parathyroid
Adrenal Glands
Ovary (Female)
Testies (Male)
Pineal
Pancreas (Partly)

The endocrine glands react to colours as and when they are acknowledged by the brain. For instance Red is exciting to the human brain. Therefore neurotransmitters stimulate the adrenal glands to pump the adrenaline into the body.