you look here at about 500 layers of low carbon damascus(wide part left) covering a core(right)
of very high carbon damascus ( about 1,2%C). The slightly whiter zone is called carbon transition zone. Like in osmose phenomenon the zone with more carbon content gives up some carbon to the zone with less carbon content.
You can see it after etching, and more important you can feel it while wet grinding the blade. This transition zone is sometimes much harder than the rest of the blade.