The earliest version of Space Invaders was a cocktail table version and came in black and white only. When the arcade classic made the leap from Japan to the US, it was transformed into an upright arcade cabinet; Part of this transformation was adding color to the display.
Because color displays were expensive and the original game did not support color codes, Midway Games US designers became creative. To make the simple game even more attractive, they opted for a mirror bounce display. The CRT monitor was actually in the closet behind the game controls and was aimed directly at the ceiling, where the images currently displayed were reflected by a mirror towards a painted backdrop to increase game depth. In addition, colored cellophane was layered on the screen of the CRT monitor, creating the illusion of color (in this case green and orange). The combination of painted background and cellophane enabled the display of graphics that the game computer itself could not create.
In the picture above, you can see how the output of the CRT monitor was not just colored (with green, yellow, orange, and pink cellophane tapes on this particular model), but also a picture of a city against a color It would be well a decade after the release of Space Invaders before the arcade games were even able to reproduce the painted backgrounds that revalued earlier editions of the game.
The clever design selection was a hit and marked the game. At the end of Space Invaders' production run, both the US and Japanese cabinets used the cellophane trick and painted backdrop reflex specs.