[Bug Report] The event active-change of component ColorPicker always emits color-format rbg

### Element UI version
2.14.0

### OS/Browsers version
Version 1.17.75 Chromium: 87.0.4280.88 (Official Build) (64-bit)

### Vue version
2.6.11

### Reproduction Link
https://jsfiddle.net/wf75sygx/

### Steps to reproduce
Create a the component ColorPicker and watch the output of the event active-change.
The default color-format should be hex, even if it is explicitly set to hex the output does not change.

### What is Expected?
The event data should contain the color as hex value.

### What is actually happening?
The event data contains the color as rbg value.