Jaundice would appear in the eyes before it would be seen on the hands. Any basic workup would include a blood test for bilirubin, which is the basis for jaundice, so I can't imagine your doctors would have found anything and not told you. One cause of yellow palms is carotenemia, which people get if they eat a very large amount of yellow vegetables or during large quantities of vegetable juice. Or perhaps your palm skin is just thick and looks yellowish to you. You'll need to see a doctor in person to see what this actually is, if anything.
Take care.
Dr. Rockoff