What factor strongly influences soil color according to the provided content?

The strong influence of soil color is predominantly stemming from the solubility and oxidation state of iron compounds present in the soil. In particular, iron exists in different forms, such as Fe2+ (ferrous) and Fe3+ (ferric), depending on the soil's redox conditions. The presence of Fe2+ contributes to darker soil colors, while Fe3+ can lead to reddish hues due to its oxides and hydroxides. Thus, the variation in iron solubility greatly impacts the overall coloration of the soil, helping to indicate drainage conditions and the atmospheric conditions under which the soil formed. This relationship between iron solubility and soil color is particularly useful in assessing soil profiles for agricultural practices or environmental management.

The other factors mentioned, such as water retention capacity, presence of organic matter, and soil texture, can have effects on soil characteristics, but they do not directly influence color to the same extent as the presence and state of iron compounds do.