Need suggestion - Original yellow parquet floor

GG, If it is wood parquet tiles, not sure if you can sand and change the color as your tiles may be very thin. Usually people just put a new coat of poly.

If it's original wood and hasn't been through too many aggressive refnish/sanding jobs, you can probably do a light sanding (sometimes called 'screening') and put down a new poly coat. I personally favor darker floors, as it can even out the strong grain patterns found in some of the cheaper floors. If your building has a floor covering rule and you abide by it, you may not be seeing much of it anyway.

To 300's point, different buildings put down different qualities of parquet. The floors in my apartment (built 1964, I'm the 2nd owner) were 9x9" oak, and were easily patched in a few places and sanded and stained. Friends in a 1954 building (converted to coop 1970s, they're the 4th residents) have noticeably poorer floors (larger tiles, cheaper wood, aggressive prior refinish).

If you've got a bit of closet floor you won't see much of, have the floor guy use it as a test patch.

Thanks for the input. I suggested to add vinyl on top but the contractor said if it's him, he'd rather keep the real wood flooring. Now I start to have doubts again. There are more varieties if I go with vinyl.

Wood for sure.

Are they tongue-and-groove, or just glued onto the slab?

My first apartment in New York, I tried to have the parquet screened, and the tiles (which were not tongue-and-groove) all came flying up off the slab.

I think a lighter shade would resell better than dark.

My advice would be to not add vinyl on top, but make the wood look as good as possible. Good parquet can be patched by the small strip or full tile by a competent contractor/floor person (tongue & groove or glue-down floor). If what you've got is truly a mess (>1/16"gaps between many of the strips/tiles, bad staining, too many loose tiles, or you're in front_porch's old building) pull it all up and put down a standard tongue & groove oak or maple wood strip floor.

Color is fully a preference thing: I prefer darker, but have seen some beautiful lighter 'pickled' jobs that I could be very happy with. Do it in the color/tone that makes you happy. If you have more interesting things in the apartment than the floor, nobody will notice the floor.

Pulling it up may involve "environmental issues." (Asbestos).