Simply change button color

I am trying to change color of a button. I'm injecting msg.ui_update.buttonColor = 'red';.
But it seems to be not working. What am I doing wrong here ?

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        "type": "tab",
        "label": "Flow 4",
        "disabled": false,
        "info": "",
        "env": []
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    {
        "id": "e0e370a0492f92f2",
        "type": "ui-button",
        "z": "1df2f5078ba20e02",
        "group": "93f9aaa4d3dd3be5",
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        "label": "xxxxx",
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        "emulateClick": false,
        "tooltip": "",
        "color": "",
        "bgcolor": "",
        "className": "",
        "icon": "mdi-robot-confused",
        "iconPosition": "left",
        "payload": "",
        "payloadType": "str",
        "topic": "topic",
        "topicType": "msg",
        "buttonColor": "",
        "textColor": "",
        "iconColor": "",
        "enableClick": true,
        "enablePointerdown": false,
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        "pointerdownPayloadType": "str",
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    {
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        "type": "ui-group",
        "name": "Group 1",
        "page": "94179d55f06e9dc9",
        "width": "10",
        "height": "6",
        "order": 1,
        "showTitle": true,
        "className": "",
        "visible": "true",
        "disabled": "false",
        "groupType": "default"
    },
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        "id": "94179d55f06e9dc9",
        "type": "ui-page",
        "name": "Page 1",
        "ui": "aa4a481102980b53",
        "path": "/page1",
        "icon": "home",
        "layout": "flex",
        "theme": "e553d4d8b2fc2ad7",
        "breakpoints": [
            {
                "name": "Default",
                "px": "0",
                "cols": "3"
            },
            {
                "name": "Tablet",
                "px": "576",
                "cols": "6"
            },
            {
                "name": "Small Desktop",
                "px": "768",
                "cols": "9"
            },
            {
                "name": "Desktop",
                "px": "1024",
                "cols": "12"
            }
        ],
        "order": 1,
        "className": "",
        "visible": "true",
        "disabled": "false"
    },
    {
        "id": "aa4a481102980b53",
        "type": "ui-base",
        "name": "My Dashboard",
        "path": "/dashboard",
        "appIcon": "",
        "includeClientData": true,
        "acceptsClientConfig": [
            "ui-notification",
            "ui-control"
        ],
        "showPathInSidebar": false,
        "headerContent": "page",
        "navigationStyle": "default",
        "titleBarStyle": "default",
        "showReconnectNotification": true,
        "notificationDisplayTime": 1,
        "showDisconnectNotification": true
    },
    {
        "id": "e553d4d8b2fc2ad7",
        "type": "ui-theme",
        "name": "Default Theme",
        "colors": {
            "surface": "#ffffff",
            "primary": "#0094CE",
            "bgPage": "#eeeeee",
            "groupBg": "#ffffff",
            "groupOutline": "#cccccc"
        },
        "sizes": {
            "density": "default",
            "pagePadding": "12px",
            "groupGap": "12px",
            "groupBorderRadius": "4px",
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initialize the object first

msg.ui_update = {}
msg.ui_update.buttonColor = 'red'

Or better still, use a change node.

Ps, your flow cannot be imported.

In order to make code readable and usable it is necessary to surround your code with three backticks (also known as a left quote or backquote ```)

``` 
   code goes here 
```

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See this post for more details - How to share code or flow json

got it. Thank you so much.