Sorry to hear you dislike rainbows. Version 1.1 allows for changing the icon theming. Right-click on the extension and click "Toggle Icon Theming" to revert back to a gray version of the icon. It should be available as soon as the extension is updated.

It was never the intention of this add-on to allow people to switch containers through the tab context menu. At no point in its development this was ever considered as part of its roadmap. The functionality was always limited to just the one button on the menu bar, which is what the add-on aimed for, and which it has continuously been able to do without issue. The development of this add-on is not "inactive" but rather "finished for the time being."

I'm not responsible for people's wishes for this add-on to do more than it ever intended to do, and users of this add-on aren't entitled to demand more features when they were never promised or considered. I'm only responsible for making this add-on do what it purportedly aims to do, which it already does.

More importantly, the official "Multi-Account Containers" add-on by Mozilla, and further updates to the browser itself, have made this issue — and my add-on itself — entirely obsolete. You can at this point right-click on a tab and find a menu which allows you to switch containers. You don't need anything more than the base Firefox browser and Mozilla's official add-on, which you'd need anyway since that's the only way to set containers up.

This add-on is not, and doesn't intend to be, a replacement for the official Mozilla Multi-Account Containers add-on, which is the tool you should be using to manage your Firefox containers. Switch Container will never be a container manager, as that would be out of the scope of what the add-on was made for, and would bring bloat to a piece of software intended to only do exactly what it says on the tin, nothing more, nothing less. It's therefore recommended that you install and use the Multi-Account Container add-on by Mozilla for container management.

This add-on was developed and released way before Mozilla ever added that "Reopen in Container" option in the tab context menu; a year and a half, approx. Now it only serves as the same thing but in its own button on the toolbar. Maybe that has some use to people, maybe it doesn't, but I will ultimately keep it available for legacy purposes and for people who prefer older versions of Firefox for whatever reason.