Check out the section on White Balance in your manual. That should help. If you have a work light, and it looks like you do by your other pics, then you can always point that at the ceiling of your shed and let that create a more subtle ambient light, too. You'll probably find yourself needing a tripod if your doing that though, as your exposures will be a little long for hand holding.
Anyway, I've gotta run. Mrs Bobo just bought a new picture frame, and we have a nice big print to put in it. I get to go cut the window matte-- fun! Later!