Change header color in email notifications

I'd like to change the header color in my email notifications so that my logo is readable. It appears this is controlled by “Workspace Colors & Logo,” but I’m locked out of those settings unless I upgrade to a Business account.

I have a Pro account now. Upgrading to a business account doubles my monthly subscription fee, from $12 to $24. Fine, but a Business account requires a minimum of 3 subscribers, so it will cost me an extra $60/month to change the header color in my email notifications??

I was able to add my freelance company logo during the free trial period, but I didn’t set the background color. There must be another way to change this besides setting up another free account and transferring my sheets over.