I messed around with a few different colors of stain and managed to somewhat disguise the fact that the thresholds are red oak while the floors are white oak. It's impossible to hide the grain, but the red did get somewhat subdued by the different stains I used. The threshold doesn't match the floor exactly, but it's a compatible shade so it blends in pretty well.
The Minwax stain colors I used were Provincial, which is a kind of neutral medium dark brown, and Driftwood, which looks like it has gray paint added to it. I wiped the Provincial off almost immediately but I let the Driftwood sit on there for about ten minutes before wiping. Then I put on three coats of oil-based semigloss polyurethane that we already had on hand and that made it a little shinier than I wanted it to be. But I'm sure it will get scuffed up soon enough and look more normal. I'll get some satin next time.
Here's the completely finished room. Look at those cute sconces on the sides of the windows! I am really going to enjoy spending time in here.
Damn! I just noticed it's not completely finished yet - we don't have doorknobs! Sheesh, it's always something. Okay, the doorknobs are next! I've grown so accustomed to not having doorknobs that I didn't even notice they were missing. But at least I can start unpacking everything now.