An intelligent race of shapeshifter came to settle on present day Earth, they managed to clear the custom and are placed on 24hr monitoring by MiB agents. It is illegal for them to expose their kind to us so they took on a human appearance and learn mannerisms and etiquettes before mingling with the public, they learn to excrete water in the forms of tears and drool and even appears to perspires under hot weather. I'm wondering how about blushing when the shapeshifter tried to increase their own blood pressure only to turn blue or green which could catch unwanted attention? What's the most economic and elegant way to blush like a normal person for these blue blooded shapeshifters?