It would be nice to wrap up the color discussion with a Grand Unified Theory that covers the full range of what color can add to photographs.  That theory would also have to discuss when color adds nothing or even detracts.  But it isn't easy to plot a comprehensive explanation from some scattered examples.  Being too close to specific images may interfere with seeing the whole.  

So, rather than prematurely launch an unseaworthy theory (so to speak) that quickly sinks, I am going to stall, ruminate about this for a while, and offer in the meantime a different sort of color image.  Unlike those with the greatest dynamic impact, often incorporating vibrant, saturated, contrasty colors, these are softer and gentler.  Does that mean color contributes less?  Only if stridency is the measure.  Sometimes a whisper is sufficient.

Okay.  The last is a ringer.  Reading from left to right, this image is relatively subtle, with muted colors, and softly lit. Until without warning the red yarn, more brightly lit anyway, levitates away from the bright beige patch.  That's one of the problems with Grand Unified Theories and subjective examples.