I’m back at Mudbox again, been awhile, and for the life of me I can’t figure out how to turn off the yellow selection highlighting. I’m trying to paint some landscape pieces and it’s killing me.
Sure, sure… I’m getting old, my memory’s not what it used to be! Can anyone help?
Alas, Ctrl-d did nothing that I could discern. I’m simply trying to paint on my selected object. The only workaround (or maybe it’s THE workflow? A lot different than Maya, for me) was to hide all the other objects in my scene and paint only on one piece at a time, which isn’t convenient really, but doable. I fear my workflow is all messed up here. 
Ctrl D deselects. You don’t need to select something in Mudbox to paint or sculpt on it. The object under the cursor is active when you click.
However if you don’t want to accidentally paint or sculpt on other objects as you hit the edges, you’ll need to lock them.
Thanks, guys! That did the trick. I figured it was a workflow issue, too much time in Maya and not enough time in the real world. I got my painting done now and it’s working great. 