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Why can mixing red and green filters block nearly all light?

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A circular RYB color wheel divided into twelve segments, showing a progression of colors from red, orange, and yellow to green, blue, and violet. — colour The RYB color model is being illustrated on a color wheel.

Mixing red and green filters blocks nearly all light because they operate through subtractive colour mixing, a process involving the selective absorption of specific wavelengths from a light source.1

A red filter is designed to transmit red light while absorbing other colours in the spectrum. Conversely, a green filter is designed to transmit green light while absorbing red light. When these two filters are placed together in a single beam of white light, the following occurs:1

The red filter absorbs the non-red components of the light, allowing only red light to pass through.1
The green filter then intercepts that remaining red light and absorbs it.1

Because the red filter has already removed the green and blue components, and the green filter removes the red component, no significant light is left to be transmitted, resulting in the appearance of black. This is distinct from additive mixing, where combining red and green light beams would produce yellow.1