Poor color contrast on leonardocolor.io when user prefers-color-scheme:dark

### Expected Behaviour

Good contrast on the website

### Actual Behaviour

Bad contrast on the website

### Reproduce Scenario (including but not limited to)

Visit https://leonardocolor.io/#

#### Steps to Reproduce
- scroll to **End-user personalization** heading
- Emulate `prefers-color-scheme:dark`
- observe the link is dark blue (-webkit-link, linkText, etc) on #1A1A1A


Visit https://leonardocolor.io/#, emulate prefers-color-scheme:dark, and scroll to the End-user personalization heading to inspect the affected link. Identify where that link's dark-theme styling is defined and verify that the link has good contrast against #1A1A1A in the dark preference mode.

Written by the indexing model from the issue text.