Even when no sophisticated message is intended or inferred, color can deliver an emotional bump largely independent of specific subject matter. Here are some examples that elicit emotional responses.  

The vibrant colors and polished aluminum of the plane (a T-6) and the rich reflections of the sky bear no explicit message, but elicit admiration, excitement, and anticipation.  

Reflections in the Amsterdam canal convey no editorial content, but promise the simple pleasure of experiencing a slight breeze on a warm day. 

The chair in the store window triggers memories of a child's elevated perceptions of taste: lime sherbet meets Mondrian.  Back-lit leaves evoke contentment on a warm summer evening at sunset.

The contrast between the warmth of the leaves and the chill of the new-fallen snow offers simple pleasure. The blue of boat and sky promise delight on a sunny day on a mountain lake.

Exposed utility pipes and ducts of the Centre Pompidou, colored per their functions, provoke emotions of rational contentment and admiring appreciation.   

Vivid blues and greens of the Croatian coastal view embody vitality.

The muted hues of the evening Amsterdam canal scene encourage feelings of well-being, peace, and contentment.

Finally, bright leaves excite with anticipation.  (Okay.  The motion adds to the emotional message.  But would it work in black and white?  Sure.  But would it work as well?  No.)

It doesn't matter that these images, and other equivalents, might trigger entirely different emotions in other viewers.  My point is that color in photographs can directly engender feelings independent of understanding exactly what the image portrays or says (If anything).  Sometimes color is the whole point.