Styled sidebar
The sidebar has a default color of blue. You can change it to any Hex color code.
To style the sidebar, the parent object in the body array must be of type section. Inside the sections array you can add your message type.
Example

JSON example
{
"head": {
"text": "I am a header",
"sub_head": {
"text": "I am a sub header"
}
},
"body": [
{
"type": "section",
"sidebar_color": "#bada33",
"sections": [
{
"type": "message",
"text": "I am a message"
}
]
}
]
}