Gradient Strip

See if this helps:

This was created by making a frame, creating a color gradient, then superimposing a series of 2-pt width white rectangles, using Multiple Duplicate to space them at 4 pt intervals.

These are screenshots from Scribus, so expect the final PDF to show a much smoother gradient.

First, the color strip:

Now the white rectangles, repeated:

Note: upper limit for Multiple Duplicate is 100 copies, so the process had to be repeated to finish.