let arr = [
{
id: 1,
firstName: 'John',
lastName: 'Smith'
},
{
id: 2,
firstName: 'Brady',
lastName: 'Dennis'
},
{
id: 3,
firstName: 'Sandoval',
lastName: 'Pratt'
}
];
arr.forEach(function (item) {
item.firstName = item.firstName.toLowerCase();
item.lastName = item.lastName.toLowerCase();
});
let result = parseInt('#cef1ff'.substr(1), 16) - parseInt('#110011'.substr(1), 16);
console.log('#' + result.toString(16).padStart(6, '0'));