I would say a red sharpie, but I’m guessing you want one that can come off easily and look like you never wrote anything, so I would maybe try a dry erase expo one. I hope this helps!
Explanation: The dot adds half of the value of the note to itself. For example, a dotted half note gets 3 beats - value of a half note is 2, half of 2 is 1 so 2 + 1 = 3.
