Now i got flu , and my nose secrete mucus , quest = what's the difference between yellow , green and white mucus ?

Nothing!: Great question! And common misconception, too. We used to believe that mucus color could help differentiate between viral (no antibiotics required) & bacterial (need antibiotics) infections. But studies have shown that this isn't true. So don't give any credence to mucus color. Of course, this makes it problematic for docs to determine when to prescribe b/c indiscriminate use leads to resistance.