I am wildly inconsistent.
Much of my color work is done with Micrografx Picture Publisher (a Win 98-era PS-wannabe), but I also bought Clip Studio Paint EX and use it from time to time. (having done this, I should have tried SAI by now, but for some oddball reason I keep putting it off)
Another one is Krita, which I had been following for some time (BTW, Krita not only has animation ability, but can now export its animations as GIF, MP4, MKV and one other video format I can't recall off the top of my head). This application also "plays nice" with Open Broadcaster if you do streams and like to superimpose extra windows on your video (say for example, media players).
While I have paid-up versions of Clip Studio and Anime Studio Pro (now know as Moho), I'm leaning toward doing my first experiments with animation using Krita, mostly for the sheer novelty of producing them with free software.
Other applications I have experimented with are SmoothDraw and MyPaint (both are freeware, the latter also open-source)
I'm aware of GIMP, FireAlpaca and MediBang, but have not tried them (the first because of its early rep for a clunky UI, the others simply for a lack of time for additional experimentation)
---PCJ