It begins in front of the circumvallate papilla and continues forward on the top-sides of the tongue
(but not the actual sides of the tongue
nor the middle of it either). Whenever I brush my teeth and tongue, it comes off easily with no pain nor bleeding. I hardly ever consume foods with yellow dyes in them.
Besides the yellow coating, my tongue has a normal color to it and appears fine; no pain, no swelling, no cracks, no large bump, no blisters, no bad breath, etc.