Apple juice is slightly acidic and therefore red litmus will not change color.
Blue
Apple juice is a type of citric acid so it would turn blue litmus paper redish.
Litmus paper turn to red color.
Red, due to the citric acid.
blue
Blue litmus paper would turn red in orange juice.
whenever a litmus paper turns blue to red it means the solution is acidic this definitely means apple juice is acidic
Red, showing that the solution is acidic.
Litmus is a dye extracted from lichens, a plant. Upon addition of acid, litmus turns red whilst on addition of base, litmus turns blue. Being acidic, containing citric acid, lemon juice is expected to turn violet litmus paper red.
Pink
It would remain red, red litmus paper only reacts to blue in the presence of a base. Lemon juice is acidic and thus wouldn't turn the paper a color. If blue litmus paper was used in the lemon juice it would turn red. Consequently dipping blue litmus paper in a base won't change the color because it does not react with bases, only acids.
In a neutral solution litmus has a purple color.
The litmus papers are used for checking the acidic and basic nature of any substance. That's why drop of lemon juice, which is by nature acidic, turns blue litmus into red(as the property of acidic solution is to change the color of blue litmus to red). So soap solution which is by nature basic will turn red litmus into blue (as the property of basic solution is to change the color of red litmus to blue).