饼图设置color的回调如何拿到所有的数据呢？现在只能拿到colorField对应的字段数据。🤔 [QUESTION]

### 🐛 Question description [Please make everyone to understand it]
数据格式类似于这样，我想把每条对应的color设置给饼图
` data = [
{ year: '1991', value: 3, color: 'red' },
{ year: '1992', value: 3.4, color: 'yellow' },
{ year: '1993', value: 4, color: 'white' },
]`

`color: (data) => {
console.log(data);
return data.color;
},`
但是回调函数之返回year

### 💻 Link to minimal reproduction

Please provide a link by forking these links [g2plot](https://codesandbox.io/s/g2plot-reproduction-template-gyej1) or GitHub repo. What is a minimal reproduction, and why is it required?

### 🏞 Expected result

### 🚑 Any additional [like screenshots]

* **G2Plot Version**:
* **Platform**:

The issue provides an inline data example and points to the G2Plot reproduction template, but gives no version, source file, or test. Start by reproducing the pie-chart color callback behavior in that template and trace the callback's datum contract; done means the complete datum behavior is verified in a test or its limitation is clearly documented.

Written by the indexing model from the issue text.