The length would be a bit of an issue - they're actually longer than a standard pack of playing cards, which is already a bit too bit for the modern airplane tray table. Why not go for something a little more of a compromise size between bridge and mini?
I don't recommend using a colored surface, especially as the plastic underneath is white. The problem is wear and tear - over time the printed surface can wear. This can result in chipping on the edges and (if you have large areas that are printed in full color) scratches appearing in the colored areas, which, if on the card back, are as good as card markings. If you have a mostly-white back and a face that's white at least at the edges, this becomes a non-issue.