https://www.tmz.com/2024/01/18/donald-trump-red-hand-splotches-blood-sores-paper-cut/
Looks like ink to me. I reconcile my work bank statements on airplanes to keep busy/pass time and I use a red pen. My hand always looks like that in those exact spots at the end of the flight. The pressure up there must make the ink seep out a bit.