"When it comes to color matching, there is simply no substitute for practice. And the practice will go more smoothly if you make some stain boards and understand some basic color theory to point you in the right direction." - Jeff Jewitt, Complete Illustrated Guide to Finishing.

Plywood and solid wood often take color differently. And there are individual variances in the wood itself. (Is this what you're experiencing?)

It's not an easy task and it's rarely just choosing stain #234 off the shelf. People who do color matching often make their own stains, mix several stains or tint off the shelf stains, or use glazes or toners to tweak the color during the process.

Sometimes a local independent paint store (not a big box certainly) will have a Pat or Mike at the mixing station that can custom tint a stain to match. This may be your best bet.

Your other option may be to select a nice complementary color and not kill yourself trying to get a perfect match.

"Plywood and solid wood often take color differently. And there are individual variances in the wood itself. (Is this what you're experiencing?)"
Yes - yes - yes! I have 3.5" fluted oak trim that is the biggest problem. It runs vertically at the seam and the corners atop plinth blocks. These pieces not only are very different from pc to pc, but within a single pc ( after staining) Most of the problem is the fluted trim seems to have white oak within the pieces and neither the stains nor the waterlox is giving a consistent shade of color. I understand wood is different and I actually like that natural variation, but the yellow/ green vs amber thing is very ugly.
DH wants me to waterlox the entire bar according to your directions, then deal with the fluted trims pcs after we see how it all looks.
I absolutely Love the Waterlox!!! Thank you so much. The Bar rail is going to look spectacular just using the Waterlox.
So, my question is: should I proceed using only the Waterlox everywhere, then try to add some stain/dye where needed on the fluted trim to try to blend the shades?
Removing the trim is not an option. I tried to get the Jeff Jewitt book you quoted today - no luck yet.
I appreciate any of your comments or recommendations.

As bobsmyuncle said, you may need to mix stain. But here's another technique you can use, especially if you have a color that looks correct when you spread it, but ends up too light when you wipe it. And that is to do a glaze technique.

All that a glaze technique is, is to brush on the stain and DON'T wipe it. Let it dry. Highly milled wood, like flutes in a column, have the grains so compressed and hard that stain doesn't want to soak in. The surface seems almost "burnished." If the glaze seems to be too dark, let it dry up some and then wipe it off with no pressure. You can often wipe off just enough to get the color you need. Hope this helps.

see link below for information

Brushing on a glaze is a fine technique, but it is a light application, not like staining.

Here is a link that might be useful: Glazing and glazing techniques

You can load the brush with as much stain as you need to get the color light or dark. I usually don't fuss with it much. I slap it on, let it dry up some and do some wiping. If it's still too light, let it dry for a few days and go at it again. Then topcoat with what you want.

My opinion is that glazing is a heavy technique, and results in you being able to match up and unite the stains of different areas to look all the same.

I am definitely going to use the Waterlox and understand I cannot stain over the Waterlox application. green-zueus has described the fluted trim accurately. The trim that looks red oak takes the Waterlox fine. The fluted trim that seems to have or is white oak seems to not let the waterlox soak in. A mineral spirits test as recommended by Waterlox gave the same results. I think I can mix some Zar light cherry & Waterlox together to blend these pieces of trim. I am now not sure what grit of sand paper to use to prepare these fluted trim pieces. Do I want to close those pores or open them?? Since I am out of good actual samples, I am testing the back sides of the fluted trim now - adding another variable! But, I am close and I am paying attention to you and reading what you suggest.
I have only had to purchase 1 small can of stain so far which I did just to prove to myself it wasn't correct. All the others I have had on hand from other projects.
Thanks again for all your guidance - I respect your knowledge and talents!

When I am prep sanding, I use very fine paper---like 320 grit. And don't apply much pressure because sanding hardens the fibers to some degree. Use a light touch with 320 and I think that will help you.

green-zeus - Oh thank you!!! - I was using a new 320 Norton sanding pad I had - a skinny yellow foam like thing. I had it in my painting "stuff". Who knows why or when I bought it. We have been renovating this house forever - I have so many tools and "things". The guy we bought the beautiful red oak for the body of the bar mentioned to sand very so slightly. My gut instinct was to break out this 320 grit and use it! DH says I know just enough to be really dangerous!
Thanks again! I am hoping to sand and get the area cleaned up so I can begin the scary / staining trim this weekend.

Got a big chuckle out of that last post. That foam thingy may do the job for you. Light sanding with no pressure will open the pores of the wood,a little. Good luck, as you've really been thru the mill on this project. DEFINITLY let us know how it all turns out for you.