Hue

What it is

Hue is a colour-memory challenge in the Senso collection of perceptual precision games. Each round, a single colour floods your screen for less than a second, then disappears. Your task is to recreate that colour as accurately as possible using three sliders: Hue, Saturation, and Brightness — the three axes of the HSV colour model.

The game is deliberately minimal. There are no distractions, no timers ticking on screen, and no partial cues — just the colour, the silence, and your memory. Five rounds make up a full session, giving a maximum score of 50 points. Target colours are bright and well-saturated, generated in OKLCh and displayed in sRGB, giving your perceptual system a clear but brief signal to lock onto.

Colours in Hue are generated in the OKLCh colour space, a perceptually uniform model in which equal numeric steps correspond to equal perceived differences across all hues. They are then gamut-mapped to sRGB for display, ensuring that every target is a colour your screen can render faithfully. Accuracy is measured using the CIEDE2000 colour-difference formula (Delta-E 2000, or Delta-E00), the current gold standard for quantifying how different two colours look to a human observer.

How to play

At the start of each round a colour appears and fills the entire screen. Look at it carefully — it will only be visible for a fraction of a second. Once it disappears you will see three sliders labelled Hue, Saturation, and Brightness. Drag each slider until the preview swatch matches what you remember. Hue controls the colour's position on the colour wheel (red, orange, yellow, green, blue, violet, and back to red). Saturation controls how vivid or washed-out the colour appears. Brightness controls how light or dark it is.

When you are satisfied with your match, confirm your answer to see your score for the round. Your score depends on how close your guess is to the original target colour as measured by CIEDE2000. A difference of Delta-E00 12 earns half marks (5 out of 10); a perfect match scores 10 points, and your running total is shown at the end of all five rounds.

The science

The core challenge in Hue is rooted in the nature of iconic memory — the very first stage of visual processing. When a stimulus disappears, a high-capacity but extremely short-lived sensory trace lingers in your visual system for roughly a few hundred milliseconds. George Sperling's landmark 1960 partial-report experiments were the first to measure iconic memory precisely: by cuing participants to report only a subset of a briefly flashed letter grid, Sperling demonstrated that the initial sensory store holds far more information than people can consciously report, but that it decays almost immediately. In Hue, that brief iconic trace is your best resource — which is why the colour is shown for less than a second rather than several seconds.

The difficulty compounds because colour memory degrades in a characteristic way. Even when the iconic trace fades, people retain a rough categorical sense of the colour — 'it was a muted teal' or 'something orangey-red'. This phenomenon, known as the memory colour effect and closely related to categorical perception of colour, means that recall is pulled toward the prototypical examples of basic colour categories rather than preserved as a precise perceptual value. The sliders in Hue force you to move beyond category-level recall and commit to an exact point in three-dimensional colour space, exposing every degree of imprecision.

Human colour perception rests on three types of cone photoreceptors in the retina — the L (long), M (medium), and S (short) wavelength cones — whose combined responses encode any colour as a point in a three-dimensional space. The Hue slider maps onto the dominant wavelength dimension, Saturation corresponds roughly to the ratio of chromatic to achromatic cone excitation, and Brightness reflects overall cone excitation. Complicating accurate recall is colour constancy: the visual system continuously discounts the spectral composition of the ambient illuminant so that object colours appear stable under different lighting conditions. This adaptive process is helpful in everyday life but makes absolute colour memory unreliable, because your memory of a colour includes assumptions about its lighting context that no longer apply once the stimulus is gone.

Scoring in Hue uses the CIEDE2000 formula, which computes colour difference in the CIE Lab colour space. CIE Lab was designed so that equal numeric distances correspond to equal perceived differences — a property called perceptual uniformity. In practice the 1976 CIE76 formula (simple Euclidean distance in Lab) was found to be insufficiently uniform, particularly for saturated blues and near-neutral colours. CIEDE2000 applies a series of corrections — including separate weighting functions for lightness, chroma, and hue, and a rotation term in the blue region — to bring numeric differences into close alignment with the judgements of trained colour observers. This means a Delta-E00 of, say, 5 represents a reliably similar perceptual gap regardless of whether the colours are pale yellows or vivid cyans. A note on accessibility: Hue is the one game in the Senso collection that depends directly on colour vision. Colour vision deficiency affects approximately 8% of men and 0.5% of women; if you are affected, the other four Senso games do not involve colour discrimination and are fully accessible.

Scoring explained

Each round is scored on a 0–10 scale based on the CIEDE2000 colour difference between the target colour and your guess. A perfect or near-perfect match scores 10. As the difference grows, the score decreases linearly. The half-score threshold — the difference that earns exactly 5 out of 10 — is Delta-E00 12. Beyond that threshold the score continues to fall toward zero for very large differences.

Across five rounds the maximum total is 50 points. Your cumulative score is displayed after the final round. Because CIEDE2000 is perceptually calibrated, your score is a meaningful measure of how closely your colour memory matches reality: consistent scores above 40 indicate excellent colour recall, scores in the 25–40 range reflect typical human performance, and anything below 20 suggests that categorical memory is dominating over precise perceptual recall.

Tips to improve

• Prioritise Hue first — it is the axis where human vision is most sensitive to error and where the largest score losses occur. Get the hue roughly right before fine-tuning Saturation and Brightness.
• Try to form a verbal label for the colour the instant it appears ('warm amber', 'cool slate blue') and combine it with a felt sense of its intensity and lightness. The verbal label anchors the categorical information; the felt sense preserves some of the metric detail.
• After setting the sliders, glance away from the preview swatch for a moment and then look back. Fresh glances catch colour shifts that continuous staring misses due to chromatic adaptation of your photoreceptors.
• Do not neglect the Saturation and Brightness sliders even when you feel confident about the Hue. Memory tends to compress saturation toward the middle and pull brightness toward a remembered average — consciously push your initial estimates toward the extremes and then correct back.
• Play in consistent lighting conditions. Ambient light affects how your monitor appears and can shift your perception of both the target and the preview swatch.
• If you find your scores plateauing, try the Munsell or NCS student colour-order exercises available in many art and design curricula — regular exposure to ordered colour samples genuinely improves colour discrimination over time.

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