I think the HEX is expected, so it can be used accordingly. Not sure what benefit a "Coloured element (square, circle, whatever)" would be.

You can create an alternative layout for the color field and render a div container with the color value of the field.

That is an example I created for a tutorial.

The tutorial is in German, but maybe you can Google translate it
https://www.hosteurope.de/blog/custom-fields-fuer-fortgeschrittene-parameter-und-alternative-layouts-fuer-custom-fields/

Thank you for the replies.

I was hoping to integrate that in the core, since a hex. code does not mean a lot to a regular user.

I can prepare a PR, if it has chances to get merged.

The hex code is exactly the expected result, as @C-Lodder pointed out, a coloured element does not make much sense in a generic way. To make is specific, just mkae an override and build your own element.

a coloured element does not make much sense in a generic way

Still do not understand how the hexademical code makes more sense, than the visual color.