Robert Chapin

Input fields on the WordPress admin screens have been nearly invisible since version 2.7. The problem was so severe that Matt suggested I make a plugin to override core CSS values for anyone who wanted more contrast. Following community feedback, I created this extra plugin specifically for high contrast.
This plugin adds Admin Color Scheme options that dramatically change the appearance of form fields, table rows, and background colors in the admin pages. It is not intended to follow the design principles of the built-in style sheets. If this is too much for your needs, then also consider my plugin with more subtle effects called <a href="https://wordpress.org/plugins/fix-admin-contrast/" rel="ugc">Fix Admin Contrast</a>

High Contrast Admin

Adds admin color schemes for the visually impaired.

techlogica

Adds an accessibility panel with controls for brightness, saturation, font size, spacing, and dark/light mode.

Adjust Accessibility

Adds an accessibility panel with controls for brightness, saturation, font size, spacing, and dark/light mode.

High Contrast Admin vs Adjust Accessibility