Which two possible explanations does the video give for why white light changes into colored light?

We usually view objects when they are illuminated by white light, usually sunlight or ordinary room light. White light is a mixture of all colors, in roughly equal proportions. White objects look white because they reflect back all the visible wavelengths of light that shine on them - so the light still looks white to us. Colored objects, on the other hand, reflect back only some of the wavelengths; the rest they absorb.