Originally posted by carver9
Because half of his face was green while the other half wasn't and there was no shadow. Also...both of his eyes were glowing while half of his face was green. If the planet is red, why would green even show if we are using your scenario?
That planet IS illuminated by a reddish source, that much is obvious.
Allow me to go through some physics. Objects can appear colored due to two reasons: they can emit light themselves (i.e. act as light sources) or they can reflect ambient light. The color which is seen depends on the wavelength(s) of the light which are coming off of the object.
The wavelength of green light is somewhere around 530 nm (nanometers).
Now if the object EMITS green light, you will always see it as green, because your eyes will then receive light with this ca. 530 nm wavelength. However, if the object is colored (due to pigment) but non-emitting, its observed color depends on the color of the illumination. Green pigment absorbs all the other wavelengths from the light but green which gets reflected and seen (roughly speaking). If such an object is illuminated with white light it will appear green because white light is composed of all colors. All but green gets absorbed. However, if the object is illuminated by RED/AMBER light, it cannot reflect green because there are no green wavelengths present in the incoming light to begin with. It will appear grayish.
Hulk's eyes appear green because they intrinsically emit green light whenever Hulk is angry. Just have a look at your avatar, Carver.