That is a decision to be made as part of the divorce. 
There’s no automatic formula as to how college expenses are handled. Some of the variables in deciding include the parent’s perspectives on college and the school the the kids are expected to attend. The ability of the parents to afford college expenses is a key inquiry, as are parental values about college. A court can order that college costs be paid or shared by the parents. The agreement of the parents could be placed in a contract or in a court order. Other parents choose to leave this topic unaddressed, either to be addressed in the future, or where the parental contributions towards college remain voluntary, just like with married couples.