this script uses deltaE to compare the similarity of color. about deltaE: http://zschuessler.github.io/DeltaE/

color-comparetor.js

const d3 = require('d3-color')
const deltaE = require('delta-e')

// a, b ... color code without #. (ex: FFFFFF)
function getDeltaE(a, b){
    ar = a.substr(0, 2)
    ar = parseInt(ar, 16)
    ag = a.substr(2, 2)
    ag = parseInt(ag, 16)
    ab = a.substr(4, 2)
    ab = parseInt(ab, 16)
    d3A = d3.rgb(ar, ag, ab)
    labA = d3.lab(d3A)
    console.log(labA)

    br = b.substr(0, 2)
    br = parseInt(br, 16)
    bg = b.substr(2, 2)
    bg = parseInt(bg, 16)
    bb = b.substr(4, 2)
    bb = parseInt(bb, 16)
    d3B = d3.rgb(br, bg, bb)
    labB = d3.lab(d3B)
    console.log(labB)

    return deltaE.getDeltaE00({L: labA.l, A: labA.a, B: labA.b}, {L: labB.l, A: labB.a, B: labB.b})
}

// a, b ... color code without #. (ex: FFFFFF)
function getSqurRoot(a, b){
    ar = a.substr(0, 2)
    ar = parseInt(ar, 16)
    ag = a.substr(2, 2)
    ag = parseInt(ag, 16)
    ab = a.substr(4, 2)
    ab = parseInt(ab, 16)
    console.log(`r:${ar}, g:${ag}, b:${ab}`)

    br = b.substr(0, 2)
    br = parseInt(br, 16)
    bg = b.substr(2, 2)
    bg = parseInt(bg, 16)
    bb = b.substr(4, 2)
    bb = parseInt(bb, 16)
    console.log(`r:${br}, g:${bg}, b:${bb}`)

    return Math.sqrt(Math.pow(ar-br, 2) + Math.pow(ag-bg, 2) + Math.pow(ab-bb, 2))
}

// console.log(`dist:${getSqurRoot('FFFFFF','fbfcfc')}`)
console.log(`dist:${getDeltaE('FFFFFF','e1e1e1')}`)