Guild Wars 2

I bought a shadow dye kit from the Gem Store for 125 gems, expecting to receive a shadow dye of some kind, which to my understanding isn’t being too presumptuous considering it is actually advertised as " Shadow dye kit".
However on opening my purchase what I actually received was a light tinted vomit green coloured dye, which I could have easily purchased from the trading post for a mere few silver.
Would this by any chance be a bug or have I been ripped off?

Neither.

The description reads:

Contains one random armor dye from a pool of 25 colors that includes 10 exclusive colors.

10 of the colors are shadow dyes; 15 are not. (The drop rate isn’t 40% though — you have a smaller chance of getting the shadow dyes.)