Each of the elements of 'Now Back in Stock has a CSS selector. These can be used to apply your own bespoke styling. These can be added at the top of your product.liquid file, in the <head> section of your theme.liquid or in your own style sheet, e.g:
<style>
.esc-out-of-stock-title {
color: green;
}
</style>
Will create a title something like this:
The following CSS classes and id's can be used to add customised styling to the Now Back in Stock popup.
For example
#esc-oos-form
This is the container of the whole popup.
#esc-out-of-stock-inputs
This is container of the email and SMS inputs
.esc-out-of-stock-title
This is the title of the Now Back in Stock popup
.esc-out-of-stock-subtitle
This subtitle appears under the Now Back in Stock title
.esc-sms-container
This is the container of the SMS input elements.
.esc-sms-select-country-title
This is the container of the SMS country select dropdown.
.esc-sms-input
This is the SMS input field