Fiber reactive yellow dye composition

A fiber reactive dye composition which comprises (1) a reactive dye represented by the following formula (I) in the free acid form, ##STR18## wherein Z is --CH.dbd.CH.sub.2 or --CH.sub.2 CH.sub.2 Z.sub.1 in which Z.sub.1 is a group capable of being split by the action of an alkali, and (2) at least one member selected from the group consisting of reactive dyes represented by the following formulas (II), (III) and (IV) in the free acid form, the formula (II) being ##STR19## wherein Z' is --CH.dbd.CH.sub.2 or --CH.sub.2 CH.sub.2 Z.sub.2 in which Z.sub.2 is a group capable of being split by the action of an alkali, the formula (III) being ##STR20## wherein Q is --SO.sub.2 CH.dbd.CH.sub.2 located at o-, m- or p-position against the imino group where Q in the formula (III) is located at the same position relative to imino as is the SO.sub.2 Z in the formula (I), and the formula (IV) being ##STR21## wherein Z" is --CH.dbd.CH.sub.2 or --CH.sub.2 CH.sub.2 Z.sub.3 in which Z.sub.3 is a group capable of being split by the action of an alkali, provided that the reactive dye of the formula (I) is one having --CH.sub.2 CH.sub.2 Z.sub.1 as Z when the fiber reactive dye composition comprises the reactive dye of the formula (III), and a weight ratio of at least one reactive dye of the formulas (II) to (IV) to the reactive dye of the formula (I) is from 1:100 to 50:100.