Some colors will stain, like reds... especially red !
Take the figure and if possible separate all the limbs.
Take a bowl, fill it with PURE acetone. NOT the blue stuff for nails. But PURE acetone. Pour a decent puddle in the bowl and take a cotton ball or pad and submerge it completely. Now take each separate limb and hold it at the open area with a clip or tweezers and begin to wipe the paint off towards the tip. Slow and steady, this is not a race
The first bath is to get the majority of the paint off, not all of it but just the majority of it off. Its hard to get all off on the attempt.
Once all limbs have been generally stripped of paint pour out all the old acetone and pour in fresh and do the same thing with new cotton all over again. This second is where you can make sure its clean of any old paint. Be care full not to get rubbed of paint and acetone into the figure. If so like mentioned use a Q-tip to get it out. Also use Q-tips to get into small areas if needed.
NOW this is very important, clean off with a good dish soap to remove any soaked in acetone thats left on the figure. You cant see it but its there !! Use cold or cool water.
If you don't wash the parts they will get VERY soft and fragile and possibly rip.
Once all done dry well or let sit out to dry. Put back together and BAM an all clear or unpainted toy.
Now like I said some colors will stain. I have found red is the worst. Don't even try to clear off a figure that has any shade of red... pink, orange, red etc... You ill get staining. Everything else comes off pretty clean.
Have fun
One more thing !!
The harder you rub the more it will get cloudy in that area so be gentle. Some clouding will happen so don't be disapointed if you see some no matter what.