Why Ancient People Didn't See the Color Blue

Here's a philosophical question for you. If a color doesn't have a name, can we still see it?  

Many years ago, the human eye evolved to give us the ability to see about a million colors.  

That's a lot.  

Then how come, until very recently, nobody saw or even heard of the color blue?  

Well, it's because blue just -- didn't exist yet.  

Let's find out why.