Final answer:
Claudius admits internally to his own deception by comparing it to a prostitute's use of makeup to hide her true self, illustrating his immoral actions covered by a veneer of respectability.
Step-by-step explanation:
In the aside where Claudius says, "O, 'tis too true!" he is reflecting on Polonius' words and making an internal admission about his own deception. The reference he makes to a prostitute's make-up is a comparison between the layers we apply to hide our true selves and what lies beneath them, much like a prostitute might use make-up to create a desirable facade. This alludes to the idea that Claudius has painted over his crime (the murder of his brother) with a seemingly respectable exterior. Drama and literature often use such analogies to depict how certain characters, in an effort to maintain their power or respectability, cover their immoral actions with a veneer of virtue or normalcy.