Change language and color

Hello. I love this plugin, however, I have 2 questions.

1) How do I change the output text shown to visitors. For example, if I want to change the text “checkout” to something of my choosing, where would I go about that?

2) How do I change the default colors? They are blue while my entire site is orange, how can I change this?

The page I need help with: [log in to see the link]