Colour of urine is due to urochrome, a pigment formed from Hb of dead RBCs in the blood.

Explanation

**Step-by-Step Solution:**

1. **Understanding Urochrome**: The color of urine is primarily due to a pigment called urochrome. It is important to understand what urochrome is and how it is formed.

2. **Formation of Urochrome**: Urochrome is derived from urobilin, which itself is produced from the degradation of heme. Heme is a component of hemoglobin (Hb) found in red blood cells (RBCs).

3. **Degradation Process**: When red blood cells die, the hemoglobin within them breaks down. This breakdown process involves the separation of the heme group from globin, leading to the formation of urobilin.

...