vcm

ColorBox

The script call is:

vcm.ColorBox( [ int luma = 40][ ,int format = vs.YUV444P8][, int nbh = 4][, int nbw = 6])

luma: %age brightness 1 to 99. The luma for each color box will be randomly within luma and )three fourths of luma.
format: vapoursynth all YUV formats excepting vs.YUV444PH can be specified as output format.
nbh:number of color boxes along frame height. 2 to 12 allowed.
nbw:number of color boxes along frame width. 2 to 12 allowed.

I felt abscence of colorbars function equivalent in vapoursynth for use as input in testing. ColorBox function outputs a 640 X 480 pixel frames of YUV format for 100 sec @ fps of 24. The output is not a copy of colorbars.