A compound, or a salt thereof, represented by the formula, ##STR1## wherein X is a halogen atom, Y is a group of --SO.sub.2 CH.dbd.CH.sub.2 or --SO.sub.2 CH.sub.2 CH.sub.2 Z (in which Z is a group capable of being split by the action of an alkali), A is an unsubstituted or substituted phenylene or naphthylene group, B is a cycloalkylene group of the formula, ##STR2## an arylene group of the formula, ##STR3## or an alkylene of the formula --(CH.sub.2).sub.1 --, (in which R.sub.3 and R.sub.4 are independently a hydrogen atom or a methyl, ethyl or methoxy group, n is 0, 1 or 2 and 1 is an integer of 2 to 6), R.sub.1 and R.sub.2 are independently a hydrogen atom or an unsubstituted or substituted lower alkyl group, and m is 0, 1 or 2, provided that the group Y is located at m- or p-position to the group ##STR4## when B is the arylene group, which is useful for dyeing fiber materials, particularly cellulose fiber materials, in a blue color having excellent fastness, with excellent build-up and level-dyeing properties.