Which reagent is used to produce a color change with trichlorinated compounds?

Sodium hydroxide is the correct choice for producing a color change with trichlorinated compounds. When sodium hydroxide is introduced to trichlorinated compounds, it can facilitate a reaction that leads to the release of chloride ions and other products, often resulting in a visible color change due to the formation of a new compound or complex.

In analytical chemistry and forensic analysis, the ability to visualize the presence of specific compounds through color changes is essential for identifying substances. Sodium hydroxide's role in this scenario is significant, as it can hydrolyze these chlorinated compounds, enhancing detection.

Other reagents may not show a definitive color change upon interaction with trichlorinated compounds. For instance, ferric chloride mainly interacts with phenolic compounds, while ninhydrin is primarily used for amino acids and proteins. Fast Blue B is utilized in specific reactions involving azo dyes rather than trichlorinated compounds. Therefore, sodium hydroxide stands out as the most suitable reagent for achieving a color change in this context.