I've seen a lot of tips on good error states, but I haven't seen much on best practices for when the error state field in on focus. Here is an example of a sign up form with multiple errors (CapitalOne Credit Wise). If a user tabs to or clicks on one of the error fields, the blue on focus state seems to appear behind the red error state. I would imagine that this is hard to detect for some types of visual impairments.
Does anyone know of research or best practices regarding the on focus state of an error field?