I use to work for a floor covering company and I need a little more info. If your boards are meeting side to side you can do the trial and error of mixing stain. Install 2 or 3 new pieces of hardwood ( best to use some about 4' long. Mix your stain and try it on about a 6" section of the new boards. Be sure to let it dry and then urethan it because this make the stain look different. Be sure to write the formula's down of have the sand and finish person do it. It is best to do a number of selections on the boards to have a viriety and remember nothing takes the place of age in wood. If your boards are running end to end where they meet. You will have to finger them in and refinish all wood conected or you can put one board in the opposite direction and frame the addditional rooms with the opption of staining in a different color.