I'm making a cosplay of Heather from the HTTYD Netflix series (picture- http://vignette3.wikia.nocookie.net/...20150626234658
and as you can see, she wears what are basically bulky ugg boots. I saved this pair pictured below from my old elf ranger costume, and I'd love to be able to reuse them to both save money and not toss the boots out (though sadly, the fox fur I originally stitched onto them has to go for that. Oh well). http://www.cosplay.com/photo/3239755/
The boots pictured on me are similar in style to Ugg boots with the fake sheepskin lining inside, but they're entirely synthetic and were fairly cheap boots. The outside also isn't any kind of suede like I usually see on them, it's actually pretty smooth and certainly some kind of synthetic fabric (they're also pretty soft, not stiff at all, they just pull on and flop right over when not being worn).
So, I'd like to be able to just paint or dye them to match to save on needing to make boot covers and a little less heat on my legs (these boots are already hot enough as it is), so that's where I need suggestions. All the leather paints/dyes I know of are stated to be ONLY for real leathers and suedes, and I don't know how well any kind of craft-oriented paint or that dye-na flow fabric paint I've heard of would work on these. I definitely don't want to make it look like I just slapped cheap paint on my boots or have it rub or flake off after a single convention. The only thing that's off-limits to me is heat/stovetop dyeing unless I'm doing something like, say, dipping them into a pot of tea or coffee or something else that wouldn't ruin a pot or permanently stain if spilled.
Also, would any of the paints or dyes work to colour a bit of the inside "sheepskin" lining for her rolled-down cuff? It's off-white on the inside, and if I can change the fleece colour too it saves me having to sew on a new cuff separately. I don't mind if it's not particularly soft after, long as it's not all gross and crusty-hard.