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Theory:

Synthetic indicators are indicators that are made from artificial substances. Synthetic indicators include phenolphthalein and methyl orange.
When litmus papers are used to test a neutral solution, the same result (the below pictures) occurs.
 
1.JPG
Litmus papers in neutral solutions
 
Neutral solutions are those in which the concentrations of hydrogen and hydroxide ions are the same. Examples, sodium chloride solution, sugar solutions and water.
 
Phenolphthalein indicator:
 
Phenolphthalein is colourless in an acid medium. The colour of phenolphthalein in a basic medium is pink.
 
Lawofsimilarshapes.jpg
Test for acid and base using phenolphthalein indicator
Image Credits: Image
  
Methyl orange indicator:
 
Methyl orange is pink in an acid medium. Methyl orange appears yellow in a basic medium.
 
Acid+–+Base+Indicators+Methyl+Orange+Indicator..jpg
Test for acid and base using methyl orange indicator
 
Acid-base indicators:
 
Indicators
Colour in acid
Colour in base
Litmus paper
    Blue → Red
Red → Blue
Phenolphthalein
Colourless
Pink
Methyl orange
Pink
Yellow
Reference:
https://media.sciencephoto.com/image/c0391218/800wm/C0391218-Phenolphthalein_Indicator.jpg
Reference:
https://slideplayer.com/slide/4356752/14/images/27/Acid+%E2%80%93+Base+Indicators+Methyl+Orange+Indicator..jpg