Site: Heemfit.com
After selecting a product — I want the “buy now” button text changed to “Pre-Order Now”
Also, the button color changed to #31C4FA
You will have to use javascript to change that text though that is ill advised as the button can be different for different customers.
https://help.shopify.com/en/manual/online-store/dynamic-checkout
You’d be better off making a different button specifically for Pre-order.
Merchants implementing a pre-order customization including payment capturing should review shopifys forum tutorial and understand the authorization/capture process
https://community.shopify.com/post/616469
Note: This retitling of text is also currently not solvable by using translations https://community.shopify.com/topic/477998