Final answer:
The color indicative of gross hematuria, which would be associated with acute glomerulonephritis, is cola color. This dark, reddish or brownish tint in the urine suggests the presence of red blood cells.
Step-by-step explanation:
The nurse inspecting the urine specimen of the 12-year-old boy with acute glomerulonephritis would be looking for a color change that indicates gross hematuria.
Gross hematuria is characterized by urine that has a reddish or brownish hue due to the presence of red blood cells. This can make the urine appear cola color, which would typically indicate gross hematuria.