I agree with John F. completely but here's another .03 to .04 cents worth.
Black is a highly staining grout as well as other deep colors. Thin Set will stain raw wood also.
Even lighter colors when touching raw wood briefly will stain. Period.
I have messed up numerous times and know this to be a fact. Here's a twist though and another option. Set it up, grout, and evenly rub the grout stain throughout the raw wood. It can turn out pretty cool. Then clear coat it or add more stain accordingly and clear it. No need to buy more stain if this might suit you. Better yet, Run it by the boss lady. Pin stripe it with high-vis orange if you can pass it with the wife and she digs it. Good Luck there Amigo!
PLAN D:
Here is another angle though. Cut your border trim, stain & /or clear it to your specs to finish it and install finished product. Then you can go ahead and install trim, set tile, and grout without worries
unless you slop grout all over it and don't wipe it off. Be sure to have a sponge, clean bucket of H2O, and rags while doing so. The grout will not permeate the finish on the sealed wood and will easily wipe off so you can grout the finished trim in place no worries. Just be neat and clean. And Again, be sure to wipe it all off. If you miss some little stuff no big deal. Let it dry and scrape it off like getting some burn pot scraping practice but use a plastic putty knife or gently use a metal one. NOTE: (Wife's kitchen tools, pan cake flippers, etc; work great here as long as you have kids to blame it on.) If not, Good Luck and don't get caught. Grout will shrink over time
at the wood trim but it will be minor if you seal the wood. Very fine bead of black silicone.
PLAN E:
Another option but the grout line is likely to bust up and head south with minor movement: Make a temporary ripper of whatever wood for the boarder. Gently and sparingly tack it to where the good stuff goes. Set & grout. Gently pull after completely dry and set finish trim. Install final trim with a fine bead of silicone between the trim and grout. Have your final trim already set, glued, and nailed for the perimeter and cut to fit exactly. Then glue and/or tack it into final resting place ever so delicately.
When you nail it even with a gun up against the tile and grout line
it will likely pop. But if you get lucky, in given time, you will silicone it anyway. Or you could make cuts
on a bugs nut, ......."
How big is a bugs nut, you ask?" So tight,,, that where the tile meets the trim you do not need a grout line nor caulk at the leading edge. Pretty tight and it can be done. Then you drop a Bud bottle and it hits just right.
Last time I checked I was still uncertain how big a bugs nut was and it is very difficult to verify. I'd start with a big beetle or praying mantis first. Mouse nuts would be good enough if you can spare some wiggle room. Couldn't even find the whole nut sack last time a bug flew into my eye! Options, Bro! Get -R- Done!
Have you thought about some inlays within the field? Or a boarder and the field laid on a 45?
They make black silicone. You'll do just fine!