Paint booth filters

The black would be a carbon filter, I presume. Orientation doesn't matter, and it wants to be the third (last) filter in the series. The air flows from top to bottom in the booth they sell.

Yes, at least somwhat. Since they don't say anything about which side for the black, I guess that means it doesn't matter? 

I just use a plain old furnace filter. 

Copied from the instructions for the 15x20" filter that micromark sells:

>>>>>>>>>>

Insert the filters as follows: Black carbon filter on bottom, fluffy thick filter in middle (green side down),
and thin white filter sheet on top.

<<<<<<<<<<

Does that help at all?

I probably over think and over engineer most things. The filters arrived rolled up with a rubber band, no packaging or instructions. The picture of the second stage one appears to show the blue side out. I will take the air compressor and blow air through from both sides and see if I can tell anything. 

I should have said I'm not familiar with the product you bought, I don't buy theirs.. You could ask the seller. If it is directional one would think either the product or it's packaging would be marked as such.

I buy big sheets of filter made for furnaces and cut it up. My booth vents outside so I don't really need a full clean.

Well I bought the ones in the link I posted. No frame, just filter material. 

I don't know the answer, I built my own too and use furnace filters. There are the ones that look like 3m scrub pads and then the ones that are built like big auto air filters, ones rated for organisms/bacteria and such and then just particulate filters. The more intense the filtration the more likely to be directional, but I think they are marked. Not sure what you bought, I just go to Home Depot for mine.