# Color palette generator (complementary, triadic, analogous)

> Generate complementary, analogous, triadic, split-complementary, tetradic or monochromatic color palettes from one base color, with HEX codes.

Interactive version: https://www.calcopenly.com/programming/color-palette-generator
Subject: Programming and tech calculators

Each harmony scheme turns the base color's hue around the HSL color wheel by fixed angles and keeps its saturation and lightness: 180° for complementary, ±30° for analogous, 120° and 240° for triadic, 180° ± 30° for split-complementary and 90° steps for a tetradic square. The monochromatic scheme keeps the hue and mixes the base toward black for shades and toward white for tints, in equal steps.

Designers use it to find accent colors for a brand, chart or interface. The default, #2E86C1 at hue 204.1°, gives the triadic set #2E86C1, #C12E86 and #86C12E, and its complement is #C1692E at hue 24.1°.

Equal HSL lightness does not mean equal brightness to the eye: in that triad, #86C12E has a relative luminance of 0.434 against 0.150 for #C12E86. Check text and background pairs with a contrast checker before using them.

## Inputs

- **Base color**: #RRGGBB, a CSS name, rgb(), hsl() or oklch().
- **Scheme** (options: Complementary (opposite hue), Analogous (neighboring hues), Triadic (3 hues, 120° apart), Split-complementary, Tetradic square (4 hues, 90° apart), Monochromatic tints and shades)
- **Spread**: Analogous: hues this far either side. Split-complementary: this far either side of the complement.
- **Tints and shades each**

## Results

- Palette — main result
- Hues
- Colors

## Formula

$$
\begin{aligned} H_k &= (H_0 + \Delta_k) \bmod 360^\circ \\ S_k &= S_0,\quad L_k = L_0 \\ \text{tint}_t &= C + t\,(1 - C) \\ \text{shade}_t &= C\,(1 - t) \end{aligned}
$$

## Worked examples

### Complement of red

- Base color: #FF0000
- Scheme: Complementary (opposite hue)
- **Palette: #FF0000, #00FFFF**
- **Colors: 2**
- Checked against: Python 3.8 colorsys and an exact fractions version of CSS Color 4 hslToRgb: hue 0° + 180° → (0, 1, 1)

### Triadic from red

- Base color: red
- Scheme: Triadic (3 hues, 120° apart)
- **Palette: #FF0000, #00FF00, #0000FF**
- **Hues: 0°, 120°, 240°**
- Checked against: Python 3.8 colorsys and an exact fractions version of CSS Color 4 hslToRgb: hue rotations by 120° and 240°

### Analogous from #2E86C1

- Base color: #2E86C1
- Scheme: Analogous (neighboring hues)
- Spread: 30 °
- **Palette: #2EC1B3, #2E86C1, #2E3DC1**
- Checked against: Python 3.8 fractions implementation of CSS Color 4 rgbToHsl/hslToRgb: hue 204.1° ± 30° gives (46, 193, 178.5) and (46, 60.5, 193), rounded half up

### Tetradic square from red

- Base color: #FF0000
- Scheme: Tetradic square (4 hues, 90° apart)
- **Palette: #FF0000, #80FF00, #00FFFF, #8000FF**
- Checked against: Python 3.8 fractions implementation of CSS Color 4 hslToRgb: hues 90° and 270° give a channel of exactly 127.5, rounded half up to 0x80 (float colorsys lands at 127.4999…)

### Tints and shades of grey

- Base color: #808080
- Scheme: Monochromatic tints and shades
- Tints and shades each: 2
- **Palette: #2B2B2B, #555555, #808080, #AAAAAA, #D5D5D5**
- **Colors: 5**
- Checked against: Python 3.8: 128 × (1 − t) and 128 + 127 t for t = 1/3, 2/3, rounded half up

### Grey has no hue to rotate (edge)

- Base color: #808080
- Scheme: Triadic (3 hues, 120° apart)
- **Palette: #808080, #808080, #808080**
- Checked against: Python 3.8 colorsys: saturation 0, so every hue gives (128, 128, 128)

## Questions

### How do I find the complementary color of a hex code?

Convert the color to HSL, add 180° to the hue, and convert back with the same saturation and lightness. #2E86C1 has hue 204.1°, so its complement has hue 24.1°, which is #C1692E. On this RGB-based wheel the complement of red #FF0000 is cyan #00FFFF; on the painter's red-yellow-blue wheel red pairs with green instead, so results differ between tools.

### What is the difference between triadic and split-complementary colors?

A triadic scheme uses three hues spaced evenly, 120° apart. A split-complementary scheme keeps the base and replaces its complement with the two hues on either side of it, 150° and 210° from the base when the spread is 30°. From #2E86C1 the triad is #C12E86 and #86C12E, while the split-complementary pair is #C12E3D and #C1B32E, which spreads the hues wider than an analogous set.

### What is the difference between a tint, a shade and a tone?

A tint is a color mixed with white, a shade is mixed with black, and a tone is mixed with gray. This generator makes tints and shades in equal steps: with 2 steps each, the gray #808080 gives shades #2B2B2B and #555555 and tints #AAAAAA and #D5D5D5. Mixing is done channel by channel in sRGB, so each step changes all three channels by the same fraction.

### Why don't the colors in my palette look equally bright?

HSL lightness is a formula on the RGB channels, not a measure of perceived brightness, and the eye is far more sensitive to green than to blue. The triad from #2E86C1 has equal HSL lightness, but relative luminances of 0.215, 0.150 and 0.434. For steps that look even, set lightness in OKLCH instead, which CSS Color Level 4 supports.

### Can I use palette colors for text?

Only after checking contrast. WCAG 2.2 asks for at least 4.5:1 between normal text and its background, and 3:1 for large text and interface parts. On white, #C12E86 reaches 5.25:1 and passes, #2E86C1 reaches 3.97:1 and suits only large text, and #86C12E reaches 2.17:1 and fails, so use it for fills and borders rather than text.

### How accurate is the color palette generator?

Accuracy depends on your inputs and the method's assumptions. Decimal arithmetic uses 50 significant digits, but estimates, numerical methods and source data can be less precise; the displayed rounding does not remove those limits. It is checked against 6 worked examples whose answers come from independent sources; for example, “Complement of red” is checked against Python 3.8 colorsys and an exact fractions version of CSS Color 4 hslToRgb: hue 0° + 180° → (0, 1, 1).

### Where does the method come from?

W3C CSS Color Module Level 4 §7 — HSL and the hslToRgb / rgbToHsl algorithms; Johannes Itten, The Art of Color (1961) — color contrasts and harmonic chords.

## Sources

- [W3C CSS Color Module Level 4 §7 — HSL and the hslToRgb / rgbToHsl algorithms](https://www.w3.org/TR/css-color-4/#the-hsl-notation)
- Johannes Itten, The Art of Color (1961) — color contrasts and harmonic chords