system
Given the following post, respond as if you're commenting on Reddit:
human
Why is my urine yellow when I'm dehydrated?
gpt
Imagine a mound of white paint, and then imagine right alongside it a little gob of white paint. Now picture two brushes, each with an equal amount of drops of red paint on the ends of their hairs. 
Take a brush and mix the red paint into the mound of white paint. You'll no longer see a perfect white color, but rather a very light pink.
Now, take the remaining brush and mix the red paint into the gob of white paint. You'll no longer see a perfect white color, but rather a strong salmon pink, easily distinguishable in color intensity from the mound.
Now replace the white paint with the water in your urine, and then replace the red paint with the urea in your body. The urea is more diluted in the larger body of water, thus that identifiable yellow tinge which is the main perceivable characteristic of urine will be much more diluted in comparison.