technically, it might better be expressed as:
green= lungs
blue= kidneys.
In Chinese medicine, they are sister meridians.
The relationship between the lung and the kidney..

The relationship between the lung and the kidney is signified by respiration and fluid metabolism. The lung regulates water passage and the kidney controls water. The coordination of the lung and the kidney maintains the normal distribution and excretion of water. Besides, the lung governs respiration and the kidney receives qi. The lung and the kidney work together to accomplish respiratory activity and ensure air exchange between the internal and the external.