The refractive index (RI) is probably the single most important parameter in optical systems. Chromatic dispersion, on the other hand, indicates how the RI depends on the wavelength and is central in, e.g., optical communication systems. Chromatic dispersion also plays an important role when teaching optics due to the captivating natural phenomenon of the rainbow and the white light decomposition with a prism. In this work, we propose and explore a method to characterize the refractive index of transparent liquids in the visible range without any dedicated equipment or device (such as prisms, goniometer, laser, detector, etc.).