But sometimes it's REALLY bad!

Luckily, I've found an article that gives you a straight dope on the wordless language of piss, which I've summarized below for your convenience.

Here's a summary of the article, broken down by urine quality:

• Light yellow or Clear: It's probably OK, but you may be overhydrated. Extreme overhydration can be deadly, but in general this color is fine for those not drinking unusually large volumes of liquid.
• Cloudy: Generally not a problem, provided you otherwise feel well and are symptom-free. Can be a sign of phosphaturia (cloudiness caused by low acidity), which can lead to kidney stones over time. You can test your urine for phosphaturia by adding vinegar to it, and seeing whether it turns clear in the presence of acid.
• Blue-Green: some multivitamins and over-the-counter drugs can cause this, as can certain intravenous dyes used in x-rays and CAT scans. If none of these apply to you, consult your doctor to make sure that you don't have a bacterial infection.
• Fluorescent Yellow/Orange: Eating carrots or beets can cause this, as can some drugs. A dark orange color is probably bad; unless you're on Pyridium, it means that your liver is leaking bile into your urine.
• Brown: Again, caused by certain foods (aloe, rhubarb, fava beans) as well as certain drugs. Unfortunately, this can also be a sign of a hepatitis, urinary tract infection, internal bleeding, or even cancer. Consult a doctor.
• Smelly: Good ol' asparagus piss. Foul-smelling urine is probably not an issue, but if it's really raunchy you may have an infection.
• Pink, Red or Bloody: Eating blueberries or rhubarb may turn urine pink. May also happen as a result of overtraining or taking laxatives or antipsychotics (though hopefully not all three). It's also possible that you have mercury poisoning, bruised kidneys, or bladder cancer. If your pee is red and you haven't been eating beets, get to a doctor quickly.

Blue-green?!?!?