Why blood becomes blue in nephron?

Interesting question. I've never really investigated this but I do know that minerals diffuse in and out of the loop of Henle. Whether or not oxygen is fed to the loop of Henle tissue during this process, I'm not sure.

Have you received any updates from other sources by any chance?

There are two renal veins, a left and a right. They branch off the inferior vena cava and drain oxygen-depleted blood from the kidneys.

As they enter the kidneys, each vein separates into two parts. The posterior veins assist in draining the back section of each kidney, while the anterior veins assist the front part. These veins also are responsible for draining blood from the ureter, which transports urine away from the kidneys to the urinary bladder.

These veins should not be confused with the renal aorta. Unlike veins, the renal aorta delivers oxygenated blood to the kidneys. To simplify, the aorta carries blood to the kidneys while veins move the blood away.

Because it is one of the venules in our body. In many pics, veins and venules are shown with blue color