I've never seen gray. As far as I know, the back label is the same blades as the yellow label except that there are only five blades in the package; yellow label has ten blades per package.
I don't like plastic blade boxes. It just galls me to throw away that plastic box. I'm not an environmentalist whacko, but I am an Oregonian and one of the things which appeals to me about DE shaving is how environmentally-friendly it is. DE blades are high-grade steel and I collect my used blades in a steel blade bank box which, when it's full, will be simply places as a whole into my recycle bin. A block of steel like that is highly-recyclable; steel is one of the most recyclable materials out there and recycling steel is a huge savings over making making new steel. But the multi-blade cartridges are commingled nightmare of steel and plastic that are not easily separated. Furthermore, multi-blade cartridges always come in plastic trays which are then way over-packages in over-sized boxes with glossy and metalic inks. DE blades are wrapped in small bits of paper and then can come in small cardboard boxes (such as BIC uses). But some DE blades come in these plastic boxes. Now you have a plastic box to throw away which is entirely unnecessary. And the worst of those plastic boxes, Feather included, have a slot in the back which they encourage you to put your used blades in thus creating a commingled nightmare of steel and plastic that are not easily separated. It just galls me! Oh well...
Anyway, if they do have to use those annoying plastic boxes, the least they can do is put ten blades into each box. If they'd leave out the horrible used-blade compartment, they could maybe get 12 or even 15 blades in a box.