Source code in the plain programming language

To run:
Start up.
Clear the screen.
Divide the screen width by 8 giving a bar width.
Make a bar with 0 and 0 and the bar width and the screen's bottom.
Draw the color bars using the bar.
Refresh the screen.
Wait for the escape key.
Shut down.

To divide the screen width by a number giving a width:
Put the screen's right into the width.
Divide the width by the number.

A bar is a box.

To draw a bar using a color and move it over:
Draw and fill the bar with the color.
Move the bar right the bar's width.

To draw the color bars using a bar:
Draw the bar using the black color and move it over.
Draw the bar using the red color and move it over.
Draw the bar using the green color and move it over.
Draw the bar using the blue color and move it over.
Draw the bar using the magenta color and move it over.
Draw the bar using the cyan color and move it over.
Draw the bar using the yellow color and move it over.
Draw and fill the bar using the white color.