Override inline styles for customer sign in

Site URL: https://badlab.squarespace.com

https://badlab.squarespace.com/account/frame/login

Password: temp

I'm not sure if it's possible but I want to override the inline styles for the account login frame using css or header injection.

I've change the styles in Chrome developer but can't get it to change in Squarespace css. I've attached a picture of what I'd like it to look like.

Tried this to no avail:

div[style].Dialog-container-uCx0n h1 {
  font: 'Roboto' !important;
  content: "LOGIN TO YOUR ACCOUNT" !important;
}
#button.Button-container-BtFfe{
  background-color: #ffaa00;
  colour: #000;
}

Any ideas?
Any help would be greatly appreciated.

It is in iframe, impossible to use CSS to change its style.