How to programmatically set KDE Plasma desktop wallpaper to a colour?

Like this similar question about image wallpapers asks:

How do I set the KDE desktop wallpaper to a .JPEG file from the command line?

...except that I want to set it to a colour rather than an image, as:

...allows.

Relevant

1. I ask because https://github.com/oskarsh/Yin-Yang/issues/246#issuecomment-1837211935 hasn't been implemented.

2. Transferred to here from superuser.com per this comment by a moderator regarding a request to transfer it:

   Regarding your flag to migrate this question is too old. We cannot migrate questions older than 6 months. You are free to re-ask it on Unix & Linux yourself.