Abstract: A color-developing sheet for pressure-sensitive recording sheets, said sheet comprising as a color-developing agent at least one 2,2'-bisphenolsulfone nickel salt selected from compounds of the following formula ##STR1## wherein R.sub.3, R.sub.4, R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are identical or different, and represent a hydrogen atom, a halogen atom, an alkyl group containing 1 to 10 carbon atoms, a cycloalkyl group containing 3 to 10 carbon atoms, an aralkyl group containing 7 to 11 carbon atoms, or a phenyl group, or a mixture of at least one 2,2'-bisphenolsulfone nickel salt of the above formulae (II) and (III) and at least one 2,2'-bisphenolsulfone zinc salt of the following formula ##STR2## wherein R.sub.1 and R.sub.2 are the same as R.sub.3 through R.sub.8 defined above.