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How can reagents help identify colorless substances after paper chromatography?

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What is chromatography? — chromatography Overview of the chemical technique of chromatography.

In paper chromatography, reagents are essential for identifying substances that are otherwise invisible on the filter paper. After the solvent has moved across the paper and evaporated, these reagents are applied to the surface.1

The reagents function by chemically reacting with the separated components to form new, colored compounds. Once this reaction occurs, the previously colorless substances appear as distinct, visible spots along the path of the solvent, allowing for their identification.12

In addition to color-forming reagents, modern analytical techniques may also utilize fluorescent molecules to "tag" substances, which are then detected through fluorescence spectroscopy. This method significantly increases the sensitivity of the analysis, enabling the detection of extremely small quantities of material.3