Here is a familiar object, seen through a red filter, a green filter,
and a blue filter -- but we are showing the images in black and white,
A dark area means the object doesn't reflect this color of light, while
a light gray area means that it reflects a lot of it.
The flag, seen through the green filter, is dark some places and light
others, even though no part of the flag looks green to our eyes.
Looking at the pictures, how can you tell
that some of the stripes
are red, or that the stars are on a blue background?
Adding colors
