Azo dyes have the great deal of versatility in various Industries like in cosmetics, pharmaceuticals, food, paper and textile Industries. Azo dyes are the largest group of dyes which are highly beneficial in textile Industries. They are also been used as an acid base indicator due to their ability to function as weak acids or bases. Their importance in various Industries catches our interest to work on it. Four azo dyes Naphthalene-1-ol phenyldiazene, Naphthalene-2-ol phenyldiazene, 3-methoxy benzenol phenyl diazene and Benzenolphenyldiazene were synthesized by diazotizing aniline and coupled with α-naphthol, β-naphthol, phenol and methoxy benzene. After the synthesis, these compounds were purified through column chromatography and then were characterized by the instrumental methods like UV, IR, EIMS and ¹H-NMR. In this study the effect of substituents of phenolic rings on the color of dyes were investigated.