Atari's Star Wars had a colour vector display two years before the Etak was released.

I believe a vector CRT could be color just like a raster CRT can, using three phosphors and three electron beams (sure, technically that would’ve made the monitor a vector-raster hybrid). That would’ve raised the cost even higher, which I assume was the main reason the system was monochrome. Sure, you couldn’t easily render filled geometry with a vector display, but it wouldn’t have been anywhere near feasible with a raster monitor either given the puny hardware.