Ah well I gave up and tried Gimp, here’s the easy solution:
At the menu bar, click FILE->New and choose a template that you like. You can use the current white canvas or you can change the background color by clicking the Background Color button at the Toolbox window. After choosing the color, click EDIT->Fill with BG color to replace the default background.
For the stripes, click FILTERS->Render->Pattern->Grid. At the dialog box, set the Width value to adjust the thickness and set the Spacing value to the distance the stripes from each other. To get rid of the vertical lines, unlock the Colors button and set the second color’s A-channel to zero. You now have a regular stripe pattern with even spacing.
From this tut: http://www.helium.com/items/1652320-make-how-to-stripe-pattern-tutorial