Question

what will be the colour of a red litmus paper on bringing it in contact with a drop of NaOH and dry HCl ?

Answer 1

with NaOH it will be blue and with HCl it will be red.

Answer 2

The NaOH is basic so The red litmus will turn Blue.
And
HCl is acidic so the litmus will remain red.

Hope it helps you!