There are so many colors in the world that I feel like I have no knowledge of them. Given a shade of color to me like Lavender, I would call it nothing but Pink. So if your situation is also similar to this or in case you need what is the actual name of the color you just came across, then this would surely help.
The application is called Name That Color and is developed by Chirag Mehta, which helps people to create a color on the screen (or copy-paste CSS hex# color) and find out the name of the closest matching color. Either you can get to know the name of the color using the hex codes or create your own.
In case you wish to know the name of the color that you just saw somewhere on the screen, then the tool published yesterday called ColorPix would help. Using that tool you can first find out the hex code of the color and then using that code you can actually get the name of the color that you came across.
There are so many, in fact more than 1500, colors that finding the names to all of those would be difficult, so you can also play with the drop down menu provided in the application itself.