You can Tab through the styles to select them. From Firefox 81, autocompletions based on existing classes are suggested as you type. change the display based on print media rules. Enable coloring the All-Tabs-Popup menu. change the display based on prefers-color-scheme media rules.Blink the currently selected tab on hover/mouse over.These may change from time to time according to the developer's maintenance schedule. The following is a listing of the available options which can be accessed by going to the Add-ons Manage > ColorfulTabs > Options.
Colorful Tabs for Firefox is a highly customizable add-on that makes each tab that you open a different color which makes tabs easier to distinguish from each other and it helps to make the active tab stand out against the background tabs.