If you've got a discolored wood floor, one of cheap softwood or one that's lacking in appearance, you may want to consider painting it. What kind of paint to use on a wood floor may depend on different factors? Painting a floor is more complicated than painting a wall, because floor planks aren't designed to hold paint, and foot-traffic makes it even more likely to flake off if you don't do it right. The correct materials and methods are crucial to making it last.
The floor has to be free of varnish or any other slick covering in order for the paint to adhere. Strip it down to the wood by sanding the surface. If there's just a light coat of old varnish, you may be able to get away with using a hand-sander. But for a substantial gloss on the floor, rent a floor sander to take it up. Before sanding, remove the floor trim and go over the entire floor knocking down nail heads or other obstructions.
Laying a coat of a good sealing primer will further ensure that the paint will adhere. You want a latex primer-sealer that's formulated for interior use. Ask for assistance at the hardware store about what to use. Start painting in the corner of the room furthest from the door, applying it with a brush in the direction of the planks and working your way toward the door. Lay it thickly enough to cover the whole floor, but make sure it's smooth and flat.
Buy a latex paint especially formulated for floors or decks. Floor and deck paints often come in a semi-gloss finish, because you're going to top the paint with polyurethane, you don't want that. The polyurethane will provide the shine and it will adhere better to flat paint than glossy. Use a flat floor paint and apply it in the same manner as the primer. Use two coats, completely covering the primer.
Open the polyurethane and gently stir it. Don't shake it, as that will cause bubbles to form in the gloss. Brush it onto the floor from the far corner, in slow, careful strokes, with the lines of the floor planks. Allow it to dry overnight, then buff it with fine sandpaper to dull the shine. This allows the next coat of polyurethane to stick. Apply a second coat in the same manner as the first.