Your Mouth, Tongue and Lips
What's normal: Tongues should be rosy pink, though some people have harmless "geographic tongue": red-and-white geometric patterns. Lips should be pink to deep brown, depending on your skin tone.
• Black tongue: Bismuth subsalicylate—the active ingredient in Pepto-Bismol—can blacken the tongue. Haven't taken any? Bacteria that pools on the tongue due to diabetes, antibiotic use or poor dental hygiene can darken it, too.
• Bright red tongue: You might just be low on folate and B-12, so make sure you're taking a daily multivitamin that contains those. But if your tongue is also sore and swollen, and you're having trouble eating or talking, you might have glossitis, an inflammatory condition that can be caused by an infection, an allergic reaction, dehydration and other problems. See your doctor to determine the underlying cause.
• White patches on the tongue and the insides of cheeks: You probably have thrush, an oral yeast infection that is easily remedied with a prescription medication. If the patches have been in your mouth for longer than two weeks, see a doctor. A white patch could be a harmless canker sore or a cancerous lesion.
• Pale pink to white lips: You could be anemic, meaning that you're low on healthy red blood cells. There are many causes of the different types of anemia, including heavy periods, fibroids and even taking too much aspirin or ibuprofen, so check with your doctor to identify any underlying problems before you try to treat the matter yourself with supplements.
Also... Mucus matters
Green or yellow mucus could be a sign that your immune system is fighting a cold or other infection, especially if you also have symptoms such as a cough, fever or aches. See your doctor if it persists.
What's normal: The whites of your eyes should be bright white (if you're fair) or off-white to beige (if you have dark skin).
• Yellow: That's jaundice, a sign your liver isn't working properly. Jaundice occurs when blood is overly saturated with bilirubin, a substance created as the liver breaks down old red blood cells. Bilirubin normally exits your body via your stool, but it might stick around if your liver is having trouble doing its job (because of hepatitis or another disease) or if a blockage is not letting bile, which contains bilirubin, travel from the liver to the intestines (due to gallstones, say). See your doctor immediately.
• Bright red in the white part of one eye: If it doesn't hurt and your vision's fine, that's a burst blood vessel; it should go away in a day or so. If you have eye pain or blurred vision, or the red blotch doesn't disappear, see an ophthalmologist—you might have an infection or, less likely, a condition such as glaucoma, which affects the optic nerve, impairing sight.