Is it possible to paint outside of ABS enclosure?

[Bogertophis]

You can paint it, but it probably won't stay painted very well. Every time you bump up against it you'll knock paint off...

That's what I think too- I wouldn't paint it. I'd sooner neatly tape poster board in the desired color to the main outer surfaces- poster board has a foam core & helps insulate- + you don't have the mess & fumes of painting, with all the paint chipping off later on. I'm not in love with "Contac paper" (it gives off a chemical odor) but that's another option that might be better than painting it, IMO. You can also get large decals (in a wide variety of subjects if you search) to decorate (most of?) the outside. You could do a "collage", actually, of things you like to look at. Or you could attach "peel & stick" thin cork tiles & leave it plain, or use it for photos etc. (Cork comes in light or dark brown, probably not white- but who knows?) Carpet tiles are also "peel & stick"- in many colors & they insulate- easy to cut with scissors- I've used them for some projects.