Controlling Xref Fading in AutoCAD 2010

In 2010, xref'd layers are shown faded by default. According to JTB World there is a new AutoCAD variable that controls that: XDWGFADECTL

Go to tools > options > display tab > and at the bottom right corner find FADE CONTROL. Under it is xref display.

Or, type it in, and set it as you desire (from AutoCAD sysvar reference):

XDWGFADECTL

Type:	Integer
Saved in:	Registry
Initial value:	70

Controls the dimming for all DWG xref objects.

The valid XDWGFADECTL system variable value is between -90 and 90. When XDWGFADECTL is set to a negative value, the Xref Fading feature is not turned on, but the setting is stored.

0	DWG xref objects are not faded.
>0	When the value is positive, controls the percent of fading up to 90 percent.
<0	When the value is negative, xref objects are not faded, but the value is saved for switching to that value by changing the sign.

This and a list of other new 2010 variables can be found at JTB World New 2010 Variables