Taiga is metallic, Mintgrün is a solid color. Along with Inka and Golf, Mintgrün is more intense and fits in with the color trends of the mid 70's. Gotta offer new colors to remain trendy....
It's unfortunate that car makers are not so innovative with colors now. You get a choice of white, black, red, maybe blue and a slew of grays and silvers. Almost all of them are metallic, which for a number of reasons is an inferior paint. Pretty, but not as durable as solid paints. IMHO.