Two pieces of wood from the same tree will often look different with the same colorant(stain/dye. That means there is little assurance any piece of wood, or several pieces in a door, will take stain/dye equally.

That looks like oak. There are two major different oaks, white and red. I cannot tell the variety from the pics, but it does favor red oak characteristics.

Using a formula of stain/finish on different woods will result in different colors. The difference can be significant. As in brown on one wood and purplish on another.

The only way to find out is to try different stains/dyes on scrap. Which you do not have. The only other way is to try staining/dying/finishing the top and/or bottom edges. Those are seldom seen, so making a mistake is only known by you. bThe other problem with using the edges is that the edges/ends of a wooden board can take stain/dye differently from the flat faces. That means the colors can be slightly darker/lighter.

So, you will just have to take the plunge.

I'm with Handymac on his comments.

It looks like it has some weathering damage, so it will change when you sand off this damage. Your choice of finish will also darken it somewhat.

Pigments tend to be more colorfast than dyes. But all colorants fade over time, it's just a matter of time and exposure. Minwax stains are generally a combo of both, but some colors are pigment only and some are dye only. But be aware these are intended for interior use and may fade easily. Unfortunately, I don't know of a good exterior-grade transparent stain.

I have not used Sikkens, but heard good things about it. I would just avoid things called "Spar Urethane" that generally won't make it for a whole season. All exterior clear finishes will need regular maintenance -- some more often than others.

Another option is to use a deep-base exterior paint, without added pigment. The OAG at the paint desk will tell you it can't be one. Just nod your head and ignore them. Make up a story like, "I have my own UTCs I'm going to add."

Here is a link that might be useful: Paint as a clear finish.

Thank you both so much for such excellent advice! I'll take more pictures as I go along and share when complete.