Could removing a faceup cause problems on a dyed doll?

Acetone is a solvent for many plastics including resin. The dye typically doesn't go all the way through the resin. It's possible that the acetone manages to dissolve some of that top layer of resin when you remove the face up, which could cause patches in the dye job It's not something that definitely will happen but it is possible. Especially likely if you ever leave the acetone on the doll head to soak.
Having said this you may be able to even out any lifted spots with your face up, you could color match it with an airbrush or something like this

 

It's pretty likely the acetone would remove the dye to some extent, especially if it's a very light shade, since the dye wouldn't have penetrated as far into the resin. You could try using rubbing alcohol or acetone-free nail polish remover to fix a faceup, since it's not as potent as acetone, but that could also potentially lift the dye.
From my experience dying a doll and trying to lift that dye, rubbing alcohol lifts it some, but it definitely takes some scrubbing. Acetone lifted the dye much faster and with much less elbow grease.

 

I agree with quilleth. I’ve seen people say that acetone removes dye pretty easily, which usually helps others feel more brave because the dye can be removed if it turns out badly. Rubbing alcohol is a safer bet to remove a faceup without disturbing the dye as much.

It’s a hassle but if you take careful notes about your dye mixture, you could completely wipe the head and redye it if the faceup goes wrong. I totally understand that this would make doing the faceup more stressful though.

 

I've had to clean resin that was dyed by another artist. I can confirm that they can be removed using the following solvents: 90% rubbing alcohol (needed A LOT of rubbing though), and Mr. Color Thinner (effects much more instantaneous -- dye was practically bleeding out of the head). Now I am not sure if the dye the artist used affects the removal rate or not. But as always, better to test one solvent at a time just to avoid any mishaps!

 

Stop using acetone, it's not a safe remover for resin. It's way too strong and can cause longterm issues.

The safest, easiest to get remover is rubbing alcohol/isopropyl with 90% or higher strength. It's available in most countries, either through hardware stores, pharmacies or even online. That and a magic eraser takes care of pretty much everything.

Regarding the starting question: yes, faceup removal will affect the dye job. It will at least lighten it up/make it less intense. Sometimes people use a mild solvent on purpose to even out the dye job or lighten it up overall. Isopropyl will take it off to a certain degree. Mr. Color Thinner, acetone and co. will do so a lot faster and better.

 

I'd also say the most accessible gentle faceup remover would be acetone free nail polish remover, just be mindful if it has been tinted. Even if it takes a little bit of the dye off, it can be easily blushed back on the face (or you can give it a short dip in the dye again if it's too noticeable).

 

I’ve used acetone to strip faceups before, and I’ve used it to remove dye that I wanted off to re-dye a couple bodies. Shaking a dyed part in a jar of acetone will more or less make dye disappear, so I’d tread with a lot of caution. I’ve had no luck removing dye with rubbing alcohol (I guess others are rubbing harder/letting it sit on/i don’t know what else, but I’d say that would be safer for dye, because you have to reallly try to remove dye with rubbing alcohol, versus with acetone it just happens.