The allies of Allah have no special appearance with which they differ form other people. They have no special dress from other than just being permissible. Rather, they are to be found in all categories of the nation of Muhammad (Peace and blessings of Allah be upon him). However, the Qur'aan and the Sunnah show clearly that the best people in the sight of Allah is the one with the most of Taqwa (pious practice):
"O people, we have created you from a male and a female and made you in peoples and tribes that you may know each other. Verily, the noblest of you in the sight of Allah is the greatest in righteous practice." [Holy Quran Soorah al-Hujarat (49): 13]
Abu Hurairah narrates in a Saheeh Hadeeth: "The Prophet of Allah (sallalahu alaihe wa-sallam) was asked: "Which people are the best? He said: "Those greatest in taqwa (righteous practice)"… [Bukhareee and Muslim]