Language buttons (JS, Go, Python) color makes it hard to read when selected

Our buttons in the new unified documentation for language selection (JavaScript, Go, Python) are dark blue with black text when selected, this is very hard to read. We should make a different color choice.

<img width="512" height="210" alt="Image" src="https://github.com/user-attachments/assets/fc38a8dd-540e-4456-9e5a-89d25888a5b7" />