When metal ions are added to a ligand solution, the colour change may be due to foemation of the species. You can evaporate to dryness & analyse the metal by Atomic absorption spectroscopyically.I metal isbsent then  the change in colour change may be due to change in PH .

but no coordination compound formed

Your ligand is then probably too weakly coordinating (and the coordination compound is not thermodynamically favored, the ligand dissociates readily from your metal).

Try to do the reaction using another solvent.

If the color is not coming from the ligand itself, the color change most probably arising from the coordination change happening around the metal ion center.  In some cases the complexation may be happening in the solution between the ligand and metal ion, however may be weakly as already suggested by Dr. Imre, but the in the isolated solid state they may come apart.  This can studied through the in-situ monitoring using some instrumental method e.g., UV-Vis, NMR, etc.  If we further wish to isolated the ligand bound system in the solid state we can possibly change the pH if the ligand can be ionized or the through the change of the reaction medium or temperature change.

The metal salt is coordinating to the solvent molecules which will give a colour change. Switch solvent, if you can find a solvent that the product precipitates that will help push the reaction towards the formation of the complex.

Thank you all for your suggestions. They are a use tool to work with. Once more, thank you all.