This is an accepted solution.
Nick here from Shopify.
If you are on any other plan on Shopify, the checkout cannot be customized or changed apart from some edits from within the Theme Editor which you can find out more about here.
Hope this helps!
All the best, Nick
I'm just going to chime in on here about this...
Is there any point in the future where we'll be able to do some basic CSS to match the Checkout with the theme?
I'm currently using Brooklyn and while it does offer some customization, it's extremely limited. For example, I can't change button text color or type/font.
From the screenshots below, you can see the Cart page has buttons with a gold background with white text.
However, on the Checkout page, the button instead has an awful looking black text instead (that isn't the right type either!) which destroys some of the consistency in design.
Perhaps the Devs could just add a few more basic customization options on the theme editor to satisfy this so we don't need to shell out $2000/mo...