Search text wrong colour without Firefox colour installed
The search text is not visible (black on dark blue background with catppuccin macchiato integration) without the firefox colour extension installed. Other text (eg. search suggestions) are visible, just not the currently selected search text.
Rather than defining custom styles (including integrations from different colour schemes) I think it would be better to use the styles defined by firefox and firefox colour and theme cascade that way. This reduces the chance of things breaking when firefox changes a css class, and also the maintenance requirements for the theme.
Instead of providing the catppuccin integration for example, we can inherit the colours from firefox colour and the user can install that theme from https://github.com/catppuccin/firefox