This plugin pulls all List, variables and groups from Mailchimp account then allow you to create subscription form using Form Wizard Tool.
Yes, you can. It is multi instance supported.
You can see this tutorial to get API Key from MailChimp: Click here
Yes you can choose among six different color: Black, Blue, Green, Magenta, Pink and Green.
Yes you can now enter your own color code for almost every element of this form.