They only need one color. But it has to be the one I want 
This wasnât a fashion issue. I originally wanted a very safely rated and well ventilated helmet in bright yellow for better visibility on roads and in the woods. I notice I see bicyclists yellow helmets from afar. That brand didnât have yellow, but they have a bright orange. That also is very visible and also helps avoiding hunters shooting me. So the black and blue that REI actually had didnât work for me for objective reasons.
I buy most outdoor stuff like PFD, hats, shirts, etc to be bright yellow or orange to always be the most visible. Not because I like the colors the most, but because I like staying alive the most. With drunk hunters and drunk motor boaters you donât want to blend into the background and look like a deer or water.