amis-editor 时间轴无法正常展示颜色

#### 描述问题：

amis-editor 时间轴无法正常展示颜色

#### 截图或视频：


#### 如何复现（请务必完整填写下面内容）：

1. 你是如何使用 amis 的？
npm

2. amis 版本是什么？请先在最新 beta 版本测试问题是否存在
"amis": "6.12.0-beta.0",
"amis-core": "6.12.0-beta.0",
"amis-editor": "6.12.0-beta.0",
"amis-editor-core": "6.12.0-beta.0",
"amis-formula": "6.12.0-beta.0",
"amis-widget": "^3.2.2",

3. 粘贴有问题的完整 `amis schema` 代码：
{
"type": "page",
"body": [
{
"type": "timeline",
"items": [
{
"time": "2019-02-07",
"title": "节点数据",
"color": "#ffb200"
},
{
"time": "2019-02-08",
"title": "节点数据",
"color": "#4F86F4"
},
{
"time": "2019-02-09",
"title": "节点数据",
"color": "success"
},
{
"time": "2019-02-09",
"title": "节点数据",
"color": "warning"
}
]
}
]
}

4. 操作步骤
升级后amis-editor 无法根据配置的 color 渲染出节点颜色

Reproduce the issue in amis-editor with the provided timeline schema and the listed amis 6.12.0-beta.0 packages, then inspect the timeline component entry point and its color handling. Verify the behavior for hex colors and the success/warning values; done means each timeline node renders the configured color.

Written by the indexing model from the issue text.