The reaction involving calcium gluconate and EDTA is likely the one that exhibits a color change due to complexation. Generally, EDTA (ethylenediaminetetraacetic acid) is a chelating agent that can bind metal ions, and the resulting complexes can often be colored depending on the specific metal ion involved.
In this case, if calcium ions (Ca²⁺) from calcium gluconate react with EDTA, they can form a calcium-EDTA complex. Though calcium itself does not impart significant color, the presence of other ions or factors in the solution may influence the appearance of color.
However, the overall coloristic effects are also significantly influenced by the presence of other components like magnesium sulfate (MgSO4) or any colored ions present in the system, but calcium itself typically does not lead to vivid colors.
If you're looking for a specific color change in this reaction, it may depend on additional factors such as the concentration of reactants, the presence of transition metals, and the specific conditions under which the reaction occurs. Nonetheless, the formation of the EDTA complex with metals is frequently associated with observable changes in color in many chemical contexts.