It appears in
https://material.angularjs.org/latest/demo/input
that Deep Orange A700 is used as the default 'invalid' color, used to style text indicating an input is invalid.

I'm assuming this was chosen because it meets accessibility contrast guidelines. However, the Material team has new recommendations on defaults here.

The Material Design team recommends replacing the default with:
Google Red a700 (#D50000) on light backgrounds and

ff6e6e on dark backgrounds.

FF6E6E is a value outside of the Material palette but its the closest to Red A700 that passes accessibility.

These colors will match the Material spec, but shouldn't be considered cast in stone.

Developers and designers are welcome to override these defaults, but should take care in meeting accessibility requirements within their own applications.