Hi,
1. Emails can be edited in the menu System>Emails. For each email, you'll find a "template" setting with an edit button which will open a popup where you'll be able to edit it. The template is where most of the CSS code (and thus the colors of the email) are but you will also find a bit of them in the HTML of the email.
There are many restrictions on what you can do with HTML and CSS and it's different for different email clients.
mailchimp.com/help/limitations-of-html-email/
2. The update is still "on-hold" on our end as we're getting more feedbacks from early adopters.
We'll activate the update for everyone once we know it's safe to update for everyone else, so you don't have to worry.