Bright red coral necklace

I found this bright red coral necklace this weekend on a yard sale. It was a really great yard sale because I bought lots of nice stuff for very little money.
This is the third coral necklace I have. The lock is nothing special but the coral itself is the most beautiful shade of red. And I like its lenght, its just perfect to wear.
I think I'm a hoarder, since I manage to get from every piece of jewelry more examples.
I have posted the other two on CW a while ago but I show some more pictures here so you can compare.
They are all three totally different colors: the one I bought this weekend is bright red, I have a more pink one and a dark red one.
As I already mentioned, I can see if something is coral but I have no idea about the quality or if its color is enhanced. So does anyone have an idea how you can tell if they are dyed or not?
Thanks a lot!