SORRY BUT TWENTY SOMETHING YEARS IN THE BUILDING GAME & I HAVE NEVER COME ACROSS TIMBER THAT IS ALLREADY PAINTED. Peoples choices of decoration are immense and it would be hard to sell a material that is already painted as it limits its use and seriously narrows the intended sale audience . You can however purchase pre primed timber/MDF which still leaves the final coats of paint / and colour choice to there new owner... Even if you do paint the floor yourself i would recomend that you give it two or three coats of a good hard clear floor varnish to protect the paint .
That would be nice! Just done up a room where we had to paint our fitted wooden bed and bookcase construction with primer, then 2 coats of gloss. It took a long time!! It would have been nice just to dip the whole thing in a large vat of paint 3 times!