xSoal

const form = document.querySelector("#main-form");

form.addEventListener("submit", checkValidation);

function checkValidation(e) {
  e.preventDefault();
  //...
}

const a = [
  {
    VendorCode: 'kek',
    Color: 'Черный',
    Size: '35'
  },
  {
    VendorCode: 'kek',
    Color: 'Черный',
    Size: '36'
  },
  {
    VendorCode: 'kek',
    Color: 'Белый',
    Size: '35'
  }
]


const b = [
  {
    Name: 'Белый',
    Hex: '#FFF'
  },
  {
    Name: 'Черный',
    Hex: '#000'
  }
]


function unique(arr) {
  let res = [];

  for (let el of arr) {
    if (!res.find(rl => rl.Color === el.Color)) {
      res.push(el);
    }
  }

  return res;
}


const c = unique(a).map(el => b.find(elb => elb.Name === el.Color)?.Hex)