A compound having the general formula I or a conjugate thereof, wherein various groups are as defined in the specification. A composition includes: (i) a compound having the general formula I or a conjugate thereof and (ii) at least one surfactant selected from cationic surfactants and nonionic surfactants. Also disclosed is a preparation method for the composition and a kit comprising the composition. Further disclosed is a method for identifying and differentiating erythroblasts, basophils and lymphocytes simultaneously using the composition according to the present disclosure.
