I use Autocad Lt 2011 for home projects. The other day I left a drawing up and when I came back the back ground was grey and the drawing had whites lines. Initially, I had drawn this with a simple white back ground and black lines.
 
I think a kid climbed into my seat and started pressing buttons. Can any one point me in the direction to have my colors reset?

That would be some smart kid if he actually got into Options > Display > Colors and reset your background color then saved it and quit out of options.  Maybe he should be doing the CAD work and you should be watching Sesame Street.He didn't hit the F7 (grid on/off) button maybe?

Many CAD users (myself included) have cats in the office/workspace where these types of "anomalies" can be common when active work is left onscreen.
 
Need I say more?