That is good if lighting is not an issue because visibility will be an issue.
A very dark floor contributes significantly to the glare and gloom problem where most things have a very bright side (facing the light source) and a very dark side (facing the floor). This is in contrast with a light colored floor that reflects lots of light upwards and sideways so that things do not have a very dark side due to upwards reflected light so they are more visible and visibility is not as harsh.
Due to the shine of the floor some light is reflected, but it too appears harsh.
Probably the best for visibility is a white roof, near white walls and a light grey floor with a diffusing light source like fluorescent tubes.
Apart from glare and gloom, a black floor might look very stylish, but if you want to work on building motors or something like that it would not be a pleasant environment.
Here is a link to a paint chart I found that gives the light reflectance of each color to the right of the sample.
http://www.rinnon.co.nz/Images/DuralloyColourCard.pdf
I think I remember from a flooring chart I used when epoxy coating industrial floors that about the best light grey reflected around 50%. Very dark grey was close to zero.