I have a cold/flu, but when i cough, it tastes metallic and my sputum is yellow/green.. is this bad? could it be from smoking?

Yes it could: Maybe a signal from the gods. Time to quit?

Smoking!: Ok, people often get yellow/green sputum from uri's and as long as it resolves within a week or so then patients do well. If it doesnt resolve after 7-10 days or if it gets worse then see your primary md. Smoking is bad for your lungs period. It prevents the lung from clearing out infections. And yes, it can be from smoking. The metallic taste can be from the smoking or from the current uri.