[material-ui][TextField] Filled TextField Label has insufficient colour contrast when focused

Steps to reproduce

Link to live example:
https://mui.com/material-ui/react-text-field/#basic-textfield

EDIT: Optionally, if testing the focus state of the Text Field is difficult, we can also use the one as the Select component here: https://mui.com/material-ui/react-select/#filled-and-standard-variants

Steps:

1. Focus on the Filled TextField
2. Check the input with any accessibility tools (I used both Colour Contrast Analyzer and Accessibility Insights for Web

Current behavior

Expected behavior

Colour contrast passes accessibility tests.

Context

The label on the default primary filled variant of the text field doesn't pass WCAG for the color contrast when the input is focused.
I'm not sure what's the best way to address this issue. We can either change the grey background for the filled variant of TextField or change the label colour when focused (it's set to the primary one now. If it's set to primary dark, it passes the tests).

Your environment

  Don't forget to mention which browser you used.
  Output from `npx @mui/envinfo` goes here.

Search keywords: Filled TextField Label has insufficient colour contrast when focused

Start with the linked Filled TextField example and inspect the focused label using Colour Contrast Analyzer or Accessibility Insights for Web; the Select example is an optional comparison. Done means the default primary filled TextField label passes the WCAG colour-contrast check when focused.