Bee's reaction to the color black?

For awhile now I've seen a number of bees constantly seem to be either attracted or angered to objects that had black on it somewhere. Is the bee attacking it, attracted to it, or is there no reason at all.Bee's reaction to the color black?
Most black pigments actually contain a lot of blue (it gives the appearance of depth) and bees are very sensitive to blue - they're more in tune with the violet end of the colour spectrum and can see some ultraviolet. I would guess that they're attracted.Bee's reaction to the color black?
Apparently bees take black to be a sign of danger, so they may be attacking or trying to warn off those objects.