Theme color isn't accessible with lightmode

[brunz-me]

There's an easy way and another way to fix this...

• Easy -- we can't use green. The pre-selected colors available for Nextra themes only have bright green hues that aren't accessible. We can use a different color for now.
• The other way -- go in and add some custom CSS

Available theme colors via Nextra: https://nextra.site/docs/docs-theme/theme-configuration
Test: https://webaim.org/resources/contrastchecker/?fcolor=4DE600&bcolor=FFFFFF