Don't count on RED being visible

Was just reading about the number of color blind people and that's why Firetrucks are going with the bright yellow /green. Red becomes grey to those people!!
No, it does not become grey to us people. It's still red. I don't know how to explain it, but it is not grey. Grey is grey, just like it is for you. People who do not see color at all are out there, but they are VERY rare.
Color blindness is horribly misunderstood. We do not see in black and white, we see in color just like everyone else. We just don't see them the same as everyone else.
Example: I have "general color deficiency" so I have problems across the board. The real problem becomes in non-primary colors. The primaries themselves are not too much trouble, but once you start mixing them things don't look right. Blue and Purple are basically the same color to me. Because I don't see the red correctly in the Purple. Generally, you can deduce what color something is by comparing it to other things of known colors.
Also, while we see colors, identifying them is generally the issue, not seeing them. You learn to use knowledge a lot. A "dark" firetruck is red, grass is green the sky is blue.
I caused an entire town in Texas to flip their traffic lights the right way. They hung them all so green was on top and red was on bottom. When I look at a traffic light, I don't look at the color, I look at which light is lit up. I darn near killed myself driving though that town.
Like I said, it's really hard to explain. Never having seen colors the way "normal" people do, I can't really put words around it. To me, everything looks just like it should and always has. It's you guys that see it differently

. Even if they could fix it, I probably wouldn't do it. It would turn my world upside down and inside out.