Jaundice is a physical exam finding of "yellowing of the skin" and is a manifestation of bilirubin deposition in the skin due to increased levels of direct/conjugated bilirubin in the body's circulation. Generally speaking, the bilirubin level has to increase above 2.5 to start causing noticeable jaundice. Bilirubin levels are checked by a simple blood test. Generally speaking, because of equilibration of the concentration of bilirubin in the peripheral circulation, the degree of yellowing should be even throughout the body.
However, it becomes more obvious in certain areas of the body such as the sclera (whites of the eyes) and under the tongue. It is very important, if you do have jaundice, do be evaluated by a physician and find the cause of the jaundice. Conditions that can cause jaundice are vast and include but are not limited to hemolysis, medication side effect, gallstones in the common bile duct, liver disease, pancreatic cancer to name a few. Some of these conditions are treated easier than others.
I highly recommend that you speak to your primary care physician
and determine the cause of jaundice. Blood tests as well as imaging studies such as ultrasounds and CT can be used to pinpoint the cause of jaundice. This condition should not be neglected.