Improve the color contrast according to WCAG 2.2 Level AAA

The default color contrast is low. For minimum accessibility compliance, it should be at least **7:1** according to **WCAG 2.2 Level AAA**. For optimal readability across all visual conditions, aim for a contrast ratio of at least **9:1**.

You can check and verify the color accessibility while generating ready-made accessible palettes at:
[https://tools.labinator.com/color-accessibility](https://tools.labinator.com/color-accessibility)

No files, tests, or entry points are identified in the issue. Start by locating the default color definitions and the CLI rendering path, then check the resulting palette with the linked color-accessibility tool. Done means the default contrast reaches at least 7:1, with 9:1 as the stated readability target.

Written by the indexing model from the issue text.