Also, if you have the xref layer set in your drawing to, say, blue but you change it in the actual reference to, say, yellow, that change won't show up in your drawing (which is silly, I think). Whenever I have to make changes to an xref that someone else setup (usually incorrectly) I find it's easier for me to note the insert point of the xref, detach it, save the drawing, close it, open it again, and re-insert the xref. When you work with architectural drawings that have 100+ layers in them (why?) it's a lot easier than going through the layer dialog and changing the colors to what they should be. I should probably write a routine to take care of that. Now that I've actually typed it out, it seems like an awful lot of work.