Thin-film stacks are a powerful and versatile option for the control of spectral properties. By using alternating layers of thin film materials (typically a few tens of hundreds of nanometers thick), interference effects can be used to tailor the reflectance or transmittance spectrum of a coating over the visible or infrared range, leading to versatile spectral filters. For example, with few-layer structures, it is possible to generate bandpass structures [1] or a wide variety of hues with very high saturation [2]. However, a chief drawback of this method is that the spectral properties or colour are typically fixed during fabrication. The spectral response of the stack (or the colour) depends on the indices and thicknesses of the layer materials. As thickness of each layer is fixed during deposition, the only avenue to tune the stack response becomes changing the refractive index of one or more of the layers. One option for this is to use phase-change materials (PCMs). Such materials have two or more solid phases with a large optical contrast between them, and can be rapidly and repeatedly switched between phases using an external signal, such as a laser, heater or pulsed current (Figure 1). When the index changes, the response of the stack likewise changes. A stack design exploiting such a material may yield variable spectral properties or colours depending on the phase of the PCM layer, and can be reversibly switched between crystalline and amorphous states. In this presentation, we will review the recent developments that have been carried out at institut Fresnel on thin-film components using PCM with versatile properties.