In the truest sense of the word, a neutralization reaction is a reaction between a substance that dissociates into hydrogen ions (H+) and a substance that dissociates into hydroxide ions (OH-). Blue and red litmus paper will remain unchanged when testing the products of these reactions, because they cancel the very thing they are designed to detect. Blue litmus paper will turn red when it detects the presence of hydrogen ions. Red litmus paper will turn blue when it detects the presence of hydroxide ions. Even in reactions such as the ones you have listed, the particle the litmus paper is designed to detect is eliminated, so there will be little change in the appearance of the litmus paper, if any at all. Modern pH paper is an improvement over the more traditional red and blue litmus paper in that it uses the pH color scale to cover both acid and base indication with one manila-colored strip of paper.