Let HA be the monoprotic acid. The neutralization reaction is...
HA + NaOH ==> NaA + H2O
Depending on whether or not the monoprotic acid is a strong or weak acid, different indicators would be used.
If it is a strong acid, neutralization will occur at pH = 7 and a reasonable indicator would be bromthymol blue.
If it is a weak acid, neutralization will occur at pH > 7 and a reasonable indicator would be phenol red or phenolphthalein.
The reason for suitability is based on the pH range in which the indicator changes color.