What most people understand as color blindness is that the person cannot see one color (green,red,yellow,blue) or can't see color at all.
That's not the case. Those are extreme types of color blindness.
Color is detected in the eyes through 'rods' and 'cones' that are sensitive to red/blue/green/yellow & light (aka black and white). The extreme color blind types are those whose rods of any one (or two or all) colors just dont work at all.
Then there are the 'in between' color blind types. Like myself.
You can have cones/rods to detect a color...say, green... but not AS MANY as a normal person would. There is also the deficiency in light detecting rods which can affect color tone discrimination.
For example, I can see all colors fine. But out of every color I can see only a limited range of hues/tones of it. The color grey has 42 tones between very light grey and almost black. I can only see about 12 to 14 of those tones.
The same happens for greens and reds.
I don't see 'Peach' / 'Salmon' color. For me its either yellow or orange or red in light/dark tones.
Pink cherry blossom petals I see as white. Because they are very light pink and I don't register such a weak tone of red.
Now, if you are female and you're seeing colors others do not agree with but they are related (school bus as orange rather than yellow) you may be a tetrachromat. This means your vision is 100% good color wise but you are very sensitive to UV portions of the light spectrum... so instead of seeing the 42 tones that most people see per color, you can see about 50. Tetrachromacy only happens in females.