Very nice extension! Sometimes the first image on a page is briefly displayed in color, maybe it's my computer (Firefox under Linux). Is something like this also possible for Android?

it takes a bit of time to put filters over website so it is normal to have that but I will see what I can do with it

and

androids do usually have a greyscale mode on the devices preinstalled, I can work around a bit to make it compatible with firefox android as well but I think an app is what you are looking for? greyscaling particular apps right?

Your plugin for Firefox Android would be great.

Greyscale mode is an option I'm using right now.

that's great to hear, next release will be focused on this too then :)