The way mantis shrimp see is nonetheless super cool and interesting. They likely have no conception of 2D color at all, and can only sense the 12 different colors in general. Furthermore, only the midband of their eyes see color, when the eyes are moving and scanning for prey, they don't see color at all, which probably helps offload mental load for their small brains. Once they do see something, they then stop moving their eyes to determine the color of what they're looking at.
Also, mantis shrimp have 6 more photoreceptors in addition to the 12 colored ones, to detect polarized light. They likely see them the same way that they see color, so they probably don't consider them anything different than wavelength which is what we interpret as color.
Ed Yong's An Immense World has a section on this and I'd highly recommend it. The ways animals sense and perceive the world are often so different for ours and it's so fascinating.