Question: I do know that there are at least two types of yellow light: a light of a single wavelength of ~580 nm and a combination of green light and red light. (Technically, there could be more yellow light.) And the following two figures are making me confused.

[![Yellow, red and green reflected (from https://slideplayer.com/slide/12783633/)](https://i.stack.imgur.com/NThcwm.png)](https://i.stack.imgur.com/NThcwm.png)
[![Only yellow reflected (from https://slideplayer.com/slide/4611001/)](https://i.stack.imgur.com/w56LDm.png)](https://i.stack.imgur.com/w56LDm.png)

Are red and green light reflected from banana? What wavelengths of white light does a banana reflect?

Answer: 
Narrow-band yellow is indeed [metameric](https://en.wikipedia.org/wiki/Metamerism_(color)) to some wavelength combinations like green/red, green/yellow/orange/red etc.. But if you see a yellow-reflecting surface, you can be sure\* that its reflectance spectrum is not just a narrow-band yellow. It must be a broadband green/yellow/orange/red reflector. If you find an actual surface that has a narrow peak of reflectance at the yellow wavelength and nothing else, this surface will look dark brown, because it reflects only the tiny portion of light incident on it, compared to a broadband reflector.

So, the short answer is that the figure on the right is grossly misleading, and a banana reflects much more wavelengths than just the yellows.

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\*Unless it's fluorescing with a narrow-band yellow, which would be unusual
In simplified terms, the left hand image is true of a pure white or chrome banana and is not correct. Right-hand image is correct, of all wavelengths reflected, 580nm reflects the most and comparatively speaking the other wavelengths are partially absorbed.
The simplification of the diagrams requires you see them in conceptual terms. Technically, neither are accurate.