indicator background color

How do you change the background color of a custom indicator (in a separate window), so not on the chart?

Many have asked similar questions on here, but this one's never answerred..

Place a big rectangle (exceeds the limits of the subwindow) and color it.

phy:

Place a big rectangle (exceeds the limits of the subwindow) and color it.

I like your style :)

Example
Files:
akadex:
Example

thank you