Color Scheme Not Working

+++ Color Scheme not working +++

We are trying to use the color schemes but running into quite an odd issue whereas in the designer nothing is displayed correctly but only when we go to preview and click 'enable custom code' the colours display correctly.

This is rendering the designer experience is kinda useless as we can't really see how the website looks at all until we move into the Preview function

In this video for @Kaleb Jae its working just fine: https://www.loom.com/share/36c4d72d91264453af1beae10bd49a42?sid=4f9690c6-dcdb-477b-81b8-b5d43d7df7db
Which I dont really understand as the 'Designer' doesn't normally display custom code - so how does it display those for him in the video?

I saw the comment of someone else on the video explaining the issue with a video:

This isn't working for me in the same way. I set it up just like he explains here, but it won't show up on the canvas unless I click to preview and then click to enable custom code. Here's a Loom I made showing the issue:
https://www.loom.com/share/b4b04900024846e9a6434c3ee8934144