Custom Buttons/Url Links

Hello,

1. I know you can have the checkout button customized and linked to an external website for each product when its an affiliate product but can that button be customized when its a simple product or variable product as well. If so, how can that be done? Thanks!

2. Also, is it possible to for the checkout button link to change when a different variable is chosen? Example: a person click a red shirt and the checkout button send them to a different link when clicked versu someone that chooses a white shirt ?