Elia, Firsty to the image on the right.
It just doesn't work for me. I was struggling to see anything really clearly, and when my eye was drawn to the rim of the glass, searching for a focal point, there was more blurriness presented by the text reflected. Sometimes large areas of darkness add to the strength of a composition, but in this case I don't feel it does. Something doesn't feel quite balanced about the composition as a whole. The beautiful curved lines of the rim of the glass and water line are lost and diffused by the clutter of colours in the background. I don't think the colour is really the "star" of the image, because it wasn't really striking enough in my mind.
The B&W image on the left I think works better as a B&W because of the composition of the curves and the straight lines of the table. It just looks like Grandad got thirsty and has come in to get his glass of water, and not knowing that there wasn't perhaps someone there as you suggested, it lacks that 'scary' factor for me.
Sometimes when I begin experimenting with something new I end up with a mish mash in my images and they have really nothing to say, other than 'I'm trying a few things out.' I then look through them and pin point the characteristics, strengths, weaknesses, things I like/don't like. I then focus and refine what I am wanting to portray in my image, perhaps just one thing at a time, say composition, and consciously try to achieve that.
Perhaps keep working with B&W in mind and continue working with the compositional elements of the curves, straight angles, and shapes of the window reflection. Thanks for posting your image.