The term 'of color drain' is a reference to the process of etiolation, which is the process of a plant becoming pale or whitish due to lack of light. Etiolation is caused by a decrease in chlorophyll production, which is necessary for photosynthesis and the absorption of light. As a result, the plant's leaves become thin and weak, and its stems become elongated and spindly. The term 'of color drain' is used to describe this process, as it results in the plant losing its vibrant colors.