Abstract: A color changing transparent plate device comprises transparent plates facing each other with a gap between the plates, the gap being charged with a plurality of fluids having colors and relative densities different from each other and freely moving vertically and a fluid inlet/outlet device through which fluid flows into or out from the gap installed in order to hold an interface of the fluids with freely moving vertically wherein the colorless transparent is contained as the color, wherein the fluid above the interface is a gas and the fluid below the interface is a liquid, wherein the fluids above and below the interface are liquids, wherein the liquids are a transparent liquid and an opaque liquid, wherein the liquids are a colorless transparent liquid and a colored transparent liquid, wherein a spacer is installed in the gap and the spacer and the facing transparent plates are attached, and wherein a fluid inlet/outlet device is formed by a fluid inlet/outlet cylinder and a piston.