Are the tiles matte finish porcelain? If not, what are they? Do you have any idea what was spilled on the floor? Have you tried wetting the area with OxyClean solution, let soak, keep wet for 30 minutes, then wash, rinse, let dry?

What is the floor? Tile? vinyl? have you tried a scrub brush?

I believe the floor is vinyl. I have scrubbed very hard. I have no idea what exactly it is. The floor gets cleaned with vinegar and water. When I scrub no residue is left on the brush or anything. I assume it’s oil stain but then again I am not sure. Can any deposits grow on vinyl flooring?

Vinyl hmmmm? Do you happen to have a rubber mat near by that you use to stand on? Or perhaps a heat register somewhere near there? How about intense sunlight hitting this spot?

Do you have a room shot?

Good call.....vinyl can absorb color from mats and rug backing.

Make a paste of baking soda and water, apply to stain and leave overnight. This may remove the stain. How long did you leave the baking soda and vinegar on the stain?Maybe not long enough to work.

No mats or rugs. I left the vinegar and baking soda overnight and woke up early to try and scrub but nothing comes off.

How long have you owned the floor? Is that stain in front of the sink or some other place where you stand for LONG periods of time? How old is the floor?

Personally I think you might have wear through. That's when the pretty paint/pattern/colour wears off and you are left with the colour underneath.