Low-key values are the structural spine of Willem van Aelst, giving it gravity and atmosphere. Blues and teal-greys govern the palette, lending it an aquatic or atmospheric quality. Saturation is deliberately withheld - the beauty here lies in the near-monochromatic gradations rather than colour difference. Willem van Aelst gives 43.7% of the composition to a single #11100D - a decisive chromatic anchor. The highest-chroma note - #CEAC65 - appears at just 1.0%, deployed as a precision accent against the quieter ground. The full value range is 62 units: broad enough to build convincing three-dimensional form. The combination of low values, muted chroma, and compressed range is the signature of the Tonalist mode - painting as atmosphere. This is palette 5 of Willem van Aelst's sequence - a single chapter in a chromatic story told across many works.