Esthetics Looking for unusual fantasy blushing advice??

I definitely recommend some experimentation! To avoid the minty green, avoid blue-base greens and opt for one with a neutral or yellow base. Although, since your doll is already yellowed, it'll add a yellow undertone to all the colors you add on top. Generally when someone looks sickly, they get yellow, green, and purple undertones in various parts of their body. I think looking at paintings that show a somewhat sickly look, like Sargent's Madame X (you can really see the purple there!) as in paintings generally the undertones that aren't very noticeable in real life, are much more visible. Also definitely adding some purple + pink under the eyes will definitely make a sickly look! I think it'd be great to look at makeup tutorials too, so you can see the exact colors and placements!

 

I think warn gray works for this! Brown and purple too, because they give off a bit of a "bruise" look which I think works for sickly characters well enough (veins tend to be visible through pallid skin, and people with certain physical illnesses often bruise easily), especially for the nails. Pure yellow or green I wouldn't use personally, because I think it's hard to apply them subtly... and you might end up with more of an alien/goblin/plant-person look...? Especially if the resin itself already has a greenish cast.

 

I have a BW 2005 Juri who is that famous greenish mellow. She came to me with a faceup done with lavenders & delicate black lines. And lavender finger nails & lips. Like you say, I decided to "go with it" & used more lavender & pale blue purple for her body blushing followed by pearlescent powder to add an iridescent glow.
To me it's perfect for her. The purples don't declare themselves but divert the eye from the discoloration of the resin.
Definitely play around with colors on the body, where you can clean off & begin again if need be. I think you'll be happy with how shades of purple applied lightly can create the look you are thinking of. And, for a more sickly look some hints of acid yellow or chartreuse in highlights, not unlike what you see when bruises begin to heal might be considered.
Look at closeups of portrait painting to see the range of colors used to create the stylization which looks more natural as you step back from the painting. It is fascinating to realize all the colors used to recreate "flesh tones".

 

In case this gives you an idea what I mean ( though not her best photo...) /doll-profiles/pearl.5113/