WARNING: personal opinions follow.
As to ply vs lumber, ply has its place but whenever possible I use lumber. One problem with ply is the necessity to band the edges. Well, it isn't actually a necessity as long as you don't mind looking at butt ugly plywood edges :)
You don't necessarily have to fill the pores in oak, depends upon the look you want. However, with red oak,you do need to seal any end grain (in red oak, not white) as it is vey porous and will suck up paint like a sponge.
Color is quite personal but I would not try to match the floor. I'm not sure I would try to match the ET center either. I'd probably go for a dark brown but much depends upon what else you have in that room If you were replacing all wood stuff, I'd suggest keeping the wood the same in all so you have a set. What wood? Well...
Cherry is popular but I don't like it
Maple is popular but not among my favorites.
Walnut is wonderful if you like dark.
Everyone hates poplar but I like it. The heart wood is wierd but sap wood boards are readily available and if you like light woods, it looks fine.
I don't do red oak. I love white oak...to work and for its inherent characteristics but not for its looks.
Ash is sort of albino oak.
Birch is ho-hum IMO.
Hickory is under rated...hard but not hard to work; reasonable in cost; both sap & heart wood are attractive.
Mahogany - particularly quartered African mahogany - can be spectacular. Nothing wrong with dark red luan either but not as spectacular.