Mac Mail - Unable to change link colour

As part of my company branding, I've always changed any hyperlinks within my email message body copy to my company's colour.

Since the Big Sur update, I'm no longer to do this.

As long as the link colour translates to my email recipients' program preferences, my email recipients can feel fairly confident that any links I send (with my specifically branded link colour) are not spoofed messages.

Ideally, I would like to be able to set my hyperlink colour in preferences, so I do not have to do this manually; however, at this point, I'd at least like to be able to manually change the colour as I used to be able to do.

Does anyone have any suggestions on how to change the link colour manually (this does not work by the normal method of highlighting and selecting a colour like it used to), or in a preference somewhere?

Thanks so much :)