How is paper chromatography used to analyse colourless mixtures such as amino acids?

By breaking down (hydrolysing) the protein into its constituent amino acids the hydrolysed mixture is then spotted onto chromatography paper with reference samples. Since none of the amino acids have any colour the paper is removed from the solvent when the solvent front is almost at the top of the paper it is then hung in a fume cupboard to dry and sprayed with a disclosing agent which causes the amino acids to show up as coloured spots after the chromatogram is sprayed, the paper is placed in a warm oven and the amino acids show up as blue pink or brown spots OR the chromatogram is looked at under uv light since most colourless organic molecules are visible under uv