Brown Phlegm and a Runny nose?

I have been having this from about two days. The brown phlegm is only one or twice every morning. But the runny nose is through the day. Does anybody know what this is. I had been having bad headaches before and a sore throat. And diarrhea. But those things have all died done except the diarrhea.Is this something serious? Or just a springtime cold?