In this research, poly(vinylamine) (PVAm) was synthesized and employed as a son template in the preparation of colloidal CdS QDs. The colloidal CdS QD solutions were prepared with PVAm as the stabilizing polymer in a mixed solvent composed of methanol and water. The emitting colors of the prepared CdS QD colloids are tunable by varying the ratio of methanol/water and pH of the solvents. The CdS QD colloids are colorless under UV light at extremely low pH and the low ratio of methanol to water. The emitting color of the CdS QD colloids turn to yellow and orange as increasing methanol content and pH of the solvent. At high pH or when the cosolvent is dominant in methanol the CdS QD colloids show bright to deep blue emission. The optical properties of the CdS colloids have been systematically studied in terms of UV-vis and fluorescence spectrometry.