is there a way to set a background color for an article with jce editor?

You could probably do this by wrapping all the content in a div tag with a special class attribute that styles the div (best done in the Code editor), eg:

<div class="content-bg-1">

Your content...

</div>

then add the class to your template stylesheet, eg:

.content-bg-1 {

    background-color: #eee;

}

but how effective this is will depend on how your template lays out the article content.

Or is it possible to set a background color or an image as a background in a block?

Assuming you mean a column created using the Columns tool, again the best way is to use a css style in your template stylesheet, eg:

.content-bg-1 {

    background-color: #eee;

}

and then to select and apply this to the Columns using the Classes list in the Columns dialog, which I have just added in JCE Pro 2.9.21 Beta - https://www.joomlacontenteditor.net/downloads/editor/pro/development

Hello there.

How to use this Classes list in the Columns dialog? In my case it is empty. When i insert something and save, it is still empty.

Thanks.

Is the Styles list in the editor toolbar also empty?

It looks for me like in the attached pictures.

What items are available in the Classes list in the Columns dialog?

Nothing...

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