My daughter went through that at about 17 months old. I also read all that stuff and freaked myself out so I took her in just to be sure. They told me not to worry unless there was no color in it at all, if there is a yellowish or brownish tint to it then its fine and should pass. If it is white then be very concerned.
But like I always say, if you are concerned about it, call the doctor. At least they can put your fears at ease.