The cones responsive to long wave lengths (L cones) are simplistically called 'red cones', those sensitive to intermediate wave lengths (M-cones) are often called 'green cones', and those sensitive to short wavelengths (S cones) are often referred to as 'blue cones'. Red, green and blue cones are hence terms reflecting simply their peak absorbance. However, as your plot shows, there is a great amount of overlap in the absorption spectra of the red, green and blue pigments in the cones in the retina.
To your question: How can we perceive see light with wavelengths larger than 575 nm, and shorter than 445 nm
This is because the cones are sensitive to a whole range of wavelengths outside of their characteristic peak absorbance in the visual spectrum. However, the sensitivity does drop beyond the peak, so red light with wavelengths >445 nm will be perceived less and less clearly, up until the point it becomes undetectable (infrared). Likewise, shorter wavelengths than 445 will loose intensity and eventually become invisible (ultraviolet).
The green and red opsins are basically the same proteins with only a slightly shifted absorption spectrum - indeed, these opsins split late in evolution due to a tandem repeat and small point mutations.
Color vision is nonetheless very specific and millions of colors can be discerned by someone with normal trichromatic vision.
This is accomplished by color opponency:
The opponent color system has 2 channels, namely a red versus green and a blue versus yellow system. The input are the photoreceptors in the retina: red, green and blue cones. A third achromatic channel is used to code visual brightness (Fig.1.). The neurophysiological machinery is located in the retina and higher visual structures such as the lateral geniculate nucleus.

Fig. 1. Color opponency
This model is referred to as Hering's opponent color theory (Gouras, 2012). It states that the blue channel suppresses yellow (and vice versa) and red suppresses green (and vice versa). The advantage of this system sharpens color contrasts between opponent colors (Hurvich and Jameson, 1957). In other words, the broad flanks of the absorption spectra of the opsins are sharpened at their edges by opponent colors. This mechanism causes the fact that we cannot see yellowish blues or reddish greens etc. Instead we can only see mixed colors between channels, e.g., yellowish greens or reddish blues (purples).
References
- Gouras, Color Vision. In: Kolb et al., Webvision. The Organization of the retina and visual system, Utah University
- Hurvich & Jameson, Psychol Rev (1957); 64(6): 384-404