Since AutoCAD 2011 there has been a transparency property that allows you to apply transparency to objects & layers in the same way you apply colours, linetypes, and lineweights. Making it easy to create transparent hatches.
You can set opacity by layer, by block, or individually for an object.
The default setting for the transparency value for layers and objects is 0, the maximum value is 90.
Transparency set by "Bylayer"
It is recommended that the transparency setting in the layer manager is used to control visibility of transparent hatches. the hatch entitities (when listed) should report transparency set "Bylayer"
HPTRANSPARENCY (AutoCAD 2011) Sets the default transparency for new hatches and fills.
PREVIEWCREATIONTRANSPARENCY (AutoCAD 2012)
Controls the transparency of preview generated when using SURFBLEND, SURFPATCH, SURFFILLET, CHAMFEREDGE, FILLETEDGE, and the LOFT command
CETRANSPARENCY. (AutoCAD 2011) Controls the Transparency value when creating a new object
PLOTTRANSPARENCYOVERRIDE turns all transparency On or Off for all plots