expected "fill" to be a valid named color ("orange"), a hex…

Error message

expected "fill" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")

What it means

The 'fill' style key must pass color.ValidColor — a named color, hex code, or gradient. This error is returned when the fill value is invalid. Same validation pattern as stroke, applied to the shape's background fill.

Solutions

Use a named color, hex code like "#f0ff3a", or "linear-gradient(color1, color2)".
Validate with color.ValidColor before assigning s.Fill.Value.
Correct hex length/characters and color name spelling.

Example fix

// before
x.style.fill: #12345
// after
x.style.fill: #112233

Defensive patterns

Strategy: validation

Validate before calling

if !color.ValidColor(v) {
    return fmt.Errorf("fill %q is not a named color, hex code, or gradient", v)
}

Type guard

func validFill(v string) bool { return color.ValidColor(v) }

Try / catch

if err := applyStyle("fill", value); err != nil {
    if strings.Contains(err.Error(), "fill") {
        value = "transparent" // or a known-good default
    }
}

Prevention

Sanity-check hex codes for '#' prefix and correct digit count.
Run color.ValidColor on user-supplied fill values before applying.
Keep gradients in the linear-gradient(color1, color2) form.

When it happens

Trigger: Setting style 'fill' to a non-color value, e.g. `fill: transparent-red`, `fill: #12345` (bad hex), or an unsupported function form.

Common situations: Copy-pasting CSS colors that D2 doesn't parse, typos in named colors, gradients written with unsupported syntax.

Related errors

AI-assisted analysis of d2lang/d2@0d69dca6f5 (2026-08-31). Data as JSON: /api/errors/4218045ddf95800b. Report an issue: GitHub.

Appendix: source

Thrown at d2graph/d2graph.go:339

		f, err := strconv.ParseFloat(value, 64)
		if err != nil || math.IsNaN(f) || math.IsInf(f, 0) || f < 0 || f > 1 {
			return errors.New(`expected "opacity" to be a number between 0.0 and 1.0`)
		}
		s.Opacity.Value = value
	case "stroke":
		if s.Stroke == nil {
			break
		}
		if !color.ValidColor(value) {
			return errors.New(`expected "stroke" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
		}
		s.Stroke.Value = value
	case "fill":
		if s.Fill == nil {
			break
		}
		if !color.ValidColor(value) {
			return errors.New(`expected "fill" to be a valid named color ("orange"), a hex code ("#f0ff3a"), or a gradient ("linear-gradient(red, blue)")`)
		}
		s.Fill.Value = value
	case "fill-pattern":
		if s.FillPattern == nil {
			break
		}
		if !go2.Contains(d2ast.FillPatterns, strings.ToLower(value)) {
			return fmt.Errorf(`expected "fill-pattern" to be one of: %s`, strings.Join(d2ast.FillPatterns, ", "))
		}
		s.FillPattern.Value = value
	case "stroke-width":
		if s.StrokeWidth == nil {
			break
		}
		f, err := strconv.Atoi(value)
		if err != nil || (f < 0 || f > 15) {
			return errors.New(`expected "stroke-width" to be a number between 0 and 15`)
		}

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