Would drinking water make the blood thinner and brighter color?

I had my blood drawn today and the nurse mentioned that my blood was viscous and too dark in color, that I should drink more water to thin in out and make it a shade brighter.

After some google searches, I found no backup for her theory. I didn’t find very many articles regarding blood viscosity and color VS water intake. What I found instead were things like, “eating salty food damages the kidney and causes blood thickness,” “blood thickness and color have nothing to do with how much water one drinks,” “red blood means more oxygen,” “thick blood causes fatigue,” etc.

I wonder what causes my blood to be viscous and dark-colored? Do I need to drink more water? Thanks for your help.