improve:

src/__tests__/input-color.js

@@ -1,7 +1,7 @@
 import React from 'react';
 import renderer from 'react-test-renderer';
 import InputColor from '../';
-import { parseColor, hex2alpha } from '../utils';
+import { parseColor, hex2alpha, rgbaToHex } from '../utils';
 
 test('render', () => {
   expect(() =>
@@ -29,7 +29,7 @@ test('parseColor', () => {
     s: 76,
     v: 86,
     a: 20,
-    hex: '#3498db',
+    hex: '#3498db32',
     rgba: 'rgba(52,152,219,0.2)',
   });
 });
@@ -40,3 +40,7 @@ test('hex2alpha', () => {
   expect(hex2alpha('38')).toEqual(22);
   expect(hex2alpha('00')).toEqual(0);
 });
+
+test('rgbaToHex', () => {
+  expect(rgbaToHex('rgba(255, 255, 255,0.5))')).toEqual(`#ffffff80`);
+});

src/color-picker.js

@@ -10,6 +10,7 @@ import {
   rgba,
   hsv2rgb,
 } from '@swiftcarrot/color-fns';
+import { rgbaToHex } from './utils';
 
 const KEY_ENTER = 13;
 
@@ -35,7 +36,8 @@ const ColorPicker = ({ color, onChange }) => {
   }
 
   function changeAlpha(a) {
-    changeColor({ ...color, a });
+    const hex = rgbaToHex(`rgba(${r}, ${g}, ${b}, ${a / 100})`);
+    changeColor({ ...color, a, hex });
   }
 
   function changeHex(hex) {

src/utils.js

@@ -6,7 +6,7 @@ export function hex2alpha(aa) {
 
 export function parseColor(hexColor) {
   hexColor = hexColor.toLowerCase();
-  const hex = hexColor.substr(0, 7);
+  const hex = hexColor;
   const rgb = hex2rgb(hex);
   const { r, g, b } = rgb;
   const hsv = rgb2hsv(r, g, b);
@@ -15,6 +15,34 @@ export function parseColor(hexColor) {
   return { ...hsv, r, g, b, a, hex, rgba: rgba(r, g, b, a) };
 }
 
+export function trim(str) {
+  return str.replace(/^\s+|\s+$/gm, '');
+}
+
+export function rgbaToHex(rgba) {
+  let inParts = rgba.substring(rgba.indexOf('(')).split(','),
+    r = parseInt(trim(inParts[0].substring(1)), 10),
+    g = parseInt(trim(inParts[1]), 10),
+    b = parseInt(trim(inParts[2]), 10),
+    a = parseFloat(
+      trim(inParts[3].substring(0, inParts[3].length - 1)),
+    ).toFixed(2);
+  let outParts = [
+    r.toString(16),
+    g.toString(16),
+    b.toString(16),
+    Math.round(a * 255)
+      .toString(16)
+      .substring(0, 2),
+  ];
+  outParts.forEach(function (part, i) {
+    if (part.length === 1) {
+      outParts[i] = '0' + part;
+    }
+  });
+  return '#' + outParts.join('');
+}
+
 export {
   rgb2hsv,
   hsv2hex,