What is the meaning of the prefix "A" in material design color guidelines?
I look at Google's material color guidelines and can understand that 500 means the primary color. Higher values, like 900, mean "darker" versions of the primary color. Correspondingly, lower values means "lighter" versions of the primary color, like 50.
However, what about A100, A700, etc? What is the meaning of "A" prefix?
As mentioned on the page you linked, the A in front of the number stands for "Accent". The numbers are light the lower they are and darker the higher they are, just like non-accent colors.
Usage guidelines of these accent colors are as follows:
The accent should be used for the floating action button and interactive elements, such as:
- Text fields and cursors
- Text selection
- Progress bars
- Selection controls, buttons, and sliders Links