What causes the diffuse reflection of an object onto a nearby object to be colored the same color as that of the object? Assuming a light source, emitting white light,a red colored diffuse sphere lit up by the light, and a white plane below the sphere acting as the 'floor', we find the diffuse reflection of the sphere on the floor to be reddish in color, just like the sphere itself
Why does it have the exact same color as the sphere? The emitted light was white in color, so when the photons of the light source, collide and reflect from the sphere, should they not still be white, causing the diffuse reflection to instead be white? What causes the photons to take on a reddish hue?
In the case, of a black sphere as opposed to a red sphere, can we expect the same thing to happen? Will the diffuse reflection be grey-black in color as well? If, on the spot where the reflection is cast,a light grey soft shadow, lighter than the diffuse reflection were to exist, would the reflection of the sphere, 'overpower' that of the shadow, making the region darker as a result?
 A: When you shine  white light at a colored object, the light that scatters off it is missing some of its wavelengths i.e., it is tinted: this is why it appears colored to our eyes.
So now you have colored light radiating away from that object, and when it strikes a nearby object and is scattered off, the scattered light is of course still missing the same wavelengths that got absorbed by the first object.
This tints the second object to a color similar to that of the first object.
A: Surfaces do not reflect all wavelengths equally well. Objects that reflect red wavelengths better.. we simply call those “red objects”. Apples reflect the red wavelengths more and absorb the blue and yellow wavelengths more. Lemons reflect yellow wavelengths better and absorb more of the blue and red wavelengths. If objects reflected all wavelengths the same proportion, then there wouldn’t be colored objects.
This is different than how reflective it is overall. Something very reflective might reflect most of the light that hits it. Something dark and dull absorbs most light. If something is dark red and not shiny and not reflective, then we know two things about it: 1. It doesn’t reflect very much of the light that hits it, overall. Idk maybe it absorbs 80% of the light that hits it. 2. Whatever portion of light it does reflect, well that proportion is a bit higher for red wavelengths. Idk maybe it absorbs 60% of the red light that hits it and 95% of the blue and 95% of the yellow.
I’m not certain what you’re asking next. What we see will be the sum of the light that hits the surface. A grey shadow is only a shadow compared to some region next to it where there is light. You don’t really “add” a shadow to the situation. You add whatever light.
