The birthstone of July is the ruby, a unique gem, because its name is given due to its colour, not its mineral composition. What I mean is that you never truly have to say 'red' ruby, since ruby is understood to be red.
Ruby is corundum (the name of its mineral composition) - the same mineral as sapphire, which, though often thought of as blue, actually comes in every possible shade of colour, including orange, yellow, green and purple.
So here's a question. If a piece of corundum is pink, is it a ruby or a sapphire? Even esteemed gemologists cannot come to a common consensus. Those that are purists insist that it has to be red before it's a ruby. They would call it pink sapphire. The more inclusive ones believe that, as long as it is some form of red, it can be called a ruby. They would be fine with calling it pink ruby.
Of course, neither side is entirely correct nor entirely wrong. This is simply an artifact of our limitations of sight, expression and language.
The reason I brought this up was due to a recent surge in having to explain the identity of a particularly stunning pink corundum gem encased in intricately designed gold that now adorns the finger of an exceptionally beautiful lady who absolutely adores the jewel and the gentleman who gave it to her.