The prince is one of Portia's suitors, and Portia disdains him because he is black. Shakespeare uses the word devilish to indicate the association of the color black with evil. The devil is called "the prince of darkness." Portia says, "If he have the condition of a saint and the complexion of a devil, I had rather he should shrive [meaning remove her sins] me than wive me." The prince, realizing Portia's attitude, says, "Mislike me not for my complexion.” When the prince leaves, Portia says, “A gentle riddance. Draw the curtains: go. / Let all of his complexion choose me so” The Merchant of Venice addresses racism here, and in the behavior of, and attitudes toward Shylock, the Jewish moneylender.

Hello Rawdah, "Devilish" could have different connotations .Here it means his skin color is appealing in a bold way.

Hi Rawdaw, Devilish skin color.... could refer to the color red in a blushing manner. Adjective: Showing the cunning or ingenuity or wickedness typical of a devil. "devilish schemes" Playful in an appealingly bold way. Adverb: In a playfully devilish manner.