The white ones. :-). Seriously, I have no idea.
I bought them a couple of years ago when I realized that it was cheaper to buy IKEA curtains than it was to buy similar fabric on a per-m2 basis.
I just looked for a white cotton fabric with a tight weave that looked reasonably robust. Then I washed them a couple of times in 95 degree water to leach out anything that was going to leach and cut them to size. I hemmed some and didn't bother with others. They are all still fine. After each use I just throw them in the washing machine at 95 degrees again.