Simple ES6 based color class, that has 2 functions: rgbToHex and hexToRgb.

color.es6.js

class Color {
    rgbToHex (r, g, b) {
        return '#' + ((1 << 24) + (r << 16) + (g << 8) + b).toString(16).slice(1);
    }
    
    hexToRgb (hex) {
        let arr = hex.slice(1).match(/.{1,2}/g);
        return [parseInt(arr[0], 16), parseInt(arr[1], 16), parseInt(arr[2], 16)];
    }
}