P.P.S. — If you're debugging this, it would help to know what clears it up. I know that relaunching the app does, and it seems likely that rebuilding the database (with File->Rebuild Database) does, but does it also start working properly if you close the window and reopen it? Or if you switch view modes?
At around 7:00 PM yesterday (Friday), only one of the items due at 5:00 PM next Friday was colored orange. All the others were still colored blue (SAL tasks).
I tried closing and reopening the window and changing perspectives. Neither updated the tasks. Finally, I relaunched OmniFocus and the coloring was corrected.
Unfortunately, I did not try rebuilding the database and didn't have the debugging preference enable. I wish I had read this thread first. :-(
But I've got debugging enable now and will try rebuilding the database if I see this issue again.
PS - I caught a screenshot of the problem if anyone in support wants to see it. There's really not much to see though, just a couple of obviously mis-colored actions and one properly colored action, all with the same due date and time.