Question

why hydrochloric acid turns to pink after adding olive oil and mixed it?

Answer 1

$\huge{\tt{\red{}\green{A}\purple{N}\pink{S}\blue{W}\orange{E}\red{R}}}$

An aqueous solution of hydrochloric acid will neutralize the basic salt and form a precipitation of stearinic acid, which is a solid at room temperature, leaving sodium chloride in the solution. If you drop a bar of soap in HCl the stearinic acid will form a protective layer around the soap and it will not dissolve.