It has been known for some time that colors can be described by three numbers. If I show you light of a certain color and ask you to match it by combining lights of three other colors and varying their intensities, you'll typically be able to find a combination that looks indistinguishable. But the wavelengths you combine might be very different from the wavelengths I showed you. Light of the wavelength corresponding to yellow and light of the right combination of red and green wavelengths will look the same, even though they are physically quite different.[more inside]
The Chroma Upsampling Error. This incredibly detailed explanation of a common bug in DVD players will likely either bore you to tears or be gripping and utterly fascinating.