Blood in saliva
Doctor Answers (3) on Blood in saliva
I can understand your concern.
If he uses a tongue cleaner to rub and clean his tongue this can happen. It could more likely be something from the oral cavity itself. Because you could notice it aa blood itself. If it was lower down, it could have been more and brownish color.
But still get it checked out by a physician. Best regards. Dr. Anil kumar jain.