ASC tube trap full round with dark and light sides - diffusing vs absorbing

In the older model full round ASC tube traps, one half is light coloured and the other half is dark charcoal coloured. Does anyone know what the colours represent? Which of the two colours is for diffusing? Thanks.
Ah ha, okay. Were the two-color traps a limited time offering? I’ve never seen even a photo of one. I'll be setting mine back up again soon---I'll have to give them a call myself to find out what the seam side is.
At a distance of about six inches, speak into the tube trap.  Turn it 90 degrees and do it again.  The absorptive side will seemingly swallow your voice.