I consider myself very well-read on the phenomenon of thin-film interference: how it works, how it's used in lens making, etc. HOWEVER... there's one thing I don't get: Thin-film interference only occurs for one specific wavelength at any given point (according to all the sources I've read), not one specific color (a range of wavelengths), just one individual wavelength. This makes total sense based on how the phenomenon occurs, except that when I think about it, this should mean that thin films would not reflect vibrant colors. Let's say we're dealing with a thin film that has an even thickness, and only one specific wavelength is affected destructively, and another constructively. If white light shines on it, we should not see a vibrant color, we should see the white light with less of the wavelength that destructively interferes and more of the one that constructively interferes... but white light with less of one wavelength and more of another will still look like white light because we're still seeing all the other wavelengths reflected back to us. Thin film reflections should not seems colored for the same reason that white light emitted from a star seems white even though spectroscopy reveals many missing wavelengths in its spectrum. Please help me (and hopefully others as well) understand how it's possible for thin films to create colors. And on a related note, how do anti-reflection coatings work, even multi-coated ones, considering each layer is only effective for one wavelength and visible light (400-700nm) is at least 300 different wavelengths? Thank you so, so much!