This is sort of a wood species question, and a finishing question...
Last fall (before I came across this site) I ambitiously started building a farmhouse dining table from fir 2x6's pulled from a 100 yr old barn on our property. I got as far as putting the table top together (would now use a totally different technique based on what I've read here, but will know for next project) but winter set in and since the table top is in our unheated shop, it was just too cold to want to be out there sanding for the approximately one million hours it will take to turn those very rough fir planks into something resembling interior furniture.
I have decided I want to build the pedestals from the 'triple pedestal farmhouse table' on this site. However I'm not sure that I want to use the same wood from the barn, for a few reasons: it takes a LOT of searching for the right plank and a safe place to cut it out of, sanding sanding sanding, the usable planks don't come in 2x4 which is what the plan calls for I think, etc.
My question is: if I were to buy new wood to make the pedestals, would they look weird with the old wood table top? Does it have to be the same type of wood (ie. fir)? I think I will stain the table (though have toyed with using only clear polyurethane to keep the natural aged look of the table, depending on how much of that I lose when sanding). so I'm guessing if I use new wood, I would have to stain the table because it won't look aged like the table top, correct? If I used old wood, would I need to rip the 2x6's into 2x4's as per the plan, and if I did, how would I finish the cut edge to match the rough/aged look of the other edges?
You could paint the pedestal legs and finish the top another way - that could help. The other thing you could do with the new wood is to distress it (i.e. take the newness out, beat it up, put holes - small ones - in it, etc.) and use a weathered pine stain that minwax makes to help make it grey in color or weathered. Or, you can use my fav way of making new wood look old is to use the vinegar and steel wool method. Lots of recipes out there for it, pinterest is a good place to find it.
Also, if you do choose to use the 2x6 for the pedestals, you can just adjust the plan to accommodate that. I looked at the plan a long time ago, when it first arrived on the site, but I don't see any reason why you couldn't substitute the 2x6's for the 2x4's