This has happened to all, may times over. The difficult choice of choosing between a black&white -monochrome or a color version of a single photograph.
Althouth subjective, there may be many options in play, some are of primary importance while others are secondary in nature but still have a influence over the decision making process. It may be for example that a specific color in the photograph can influence the viewer in different ways, triggers an association to something or even that the combination of colors may not be complementary thus, less pleasing to the eye so we tend to choose a black and white version.
Different people have different personal preferences and most are deeply subjective especially when evaluation of personal work is in question, but there is more to that then just the simple phrase “ I prefer the black&white version”. The most common ‘trigger” to preferring a black&white version of a given photograph is being processed on a subconscious level. When we look at an image in monochrome the brain doesn’t need to process additional information regarding color and our subconscious association with each color and the relations between the colors in the photograph, but instead we concentrate on a specific detail and contrast in the image, thus giving instant feedback, so one gets an impression that the monochrome photograph left a stronger impression then the color one, even though we experience the world around us in color.
For example: This color photograph leads us to pay attention to the additional secondary yellow detail in the image, although the primary focus of attention should be the portrait of the person in the picture, ( even though the combination of having a yellow detail next to a blue background should have a strong contrast ).
In this black and white version of the same image, we are drawn immediately to the portrait because of the contrast involved between the subject and the background, between the white color of the beard and the darkness of the sky. The color image simply contains too much information in regards to the balck and white version when looked side by side.
So it may be a good idea that when you have second thoughts about a photograph of yours, try turning it into a monochrome version and see how it looks.
If you find that your image lacks pleasing colors or the colors are washed-out or the photograph exhibits blown-out highlights beyond repair, or you simply made a bad exposure, turning it to monochrome can save the image.
Give it a try, you might be surprised at the outcome.