Hi, Is having any other symptoms like cough, loose stools or vomiting? Fever indicates an infection somewhere in the body. Since his legs are cold and blue (suggests poor peripheral circulation with peripheral cyanosis), there is high chance that he is dehydrated and having low blood pressure, either from poor oral intake or as a part of infection. Kindly take him to doctor without delay, as we need urgent correction of dehydration to avoid further complications. Meanwhile, try to give frequent sips of fluids like salted rice water or ORS solution. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Muhammed Aslam T. K., Pediatrician