conditions.
As far as bleeding onto other chips, this will only happen if they are in direct contact with each other, so any type of page is fine from that point of view. The main problem of bleeding is where the red bleeds into any white areas of the chip. This is because the white parts, on both Chipcos & B&G's is just an unprinted part of the blank which will readily accept any color it comes into contact with for too long a time. Red just happens to be the worst. Particularly the red backs of Palms $5's which Jim Batten has had plenty of experience with
If in doubt, use the flips that Jim suggests. Thats what I use.

No fixed rule on what bleeds and what doesnt. Some chips can bleed left out on the table. Some actually get worse when exposed to the wrong type of plastic. The non-pvc flips we are talking about are made of mylar. It is still synthetic but from the chemistry point of view it is polyethylene rather than polythene. Try therefore to get mylar flips specifically, rather than just 'non-pvc', because you dont know what chemicals are in there otherwise. The pvc chemicals are merely there to make the pages and flips softer. Archival material, such as museums use, is often so hard and crisp it is like wafer thin glass.