What you're seeing are not 'scan lines'. This pattern is typical for a color vector monitor and is visible on real hardware (source: I own a Tempest arcade machine).
On a monochrome vector monitor, like an oscilloscope or Asteroids, there is one electron beam that draws on the single-phosphor screen, without obstructions between the beam and the screen, leaving sharp lines. There are no pixels as such (though the hardware in arcade games may be limited to moving the beam to discrete locations), the glass is just covered with a smooth layer of phosphor.
On a color vector monitor however there are three beams, and the screen has an RGB pattern of color sub-pixels. In between the electron guns and the screen is a 'shadow mask'. This is basically a plate with holes, positioned such that the 'blue' beam can only hit the blue subpixels, and likewise for the other colors.
What you see in the pictures is the result of the beams sweeping over that mask and interacting with the small dots of colored phosphor on the glass.
The CRT of a color vector game is just a standard television CRT. The electronics are very different however.
On a monochrome vector monitor, like an oscilloscope or Asteroids, there is one electron beam that draws on the single-phosphor screen, without obstructions between the beam and the screen, leaving sharp lines. There are no pixels as such (though the hardware in arcade games may be limited to moving the beam to discrete locations), the glass is just covered with a smooth layer of phosphor.
On a color vector monitor however there are three beams, and the screen has an RGB pattern of color sub-pixels. In between the electron guns and the screen is a 'shadow mask'. This is basically a plate with holes, positioned such that the 'blue' beam can only hit the blue subpixels, and likewise for the other colors.
What you see in the pictures is the result of the beams sweeping over that mask and interacting with the small dots of colored phosphor on the glass.
The CRT of a color vector game is just a standard television CRT. The electronics are very different however.