spectreconsole/spectre.console · error · InvalidOperationException

Invalid hex color '#{hex}'.

Error message

Invalid hex color '#{hex}'.

What it means

ParseHexColor completed without throwing but the hex string was empty or had a length other than 3 or 6, so no Color could be produced. Reports 'Invalid hex color #{hex}.'

Source

Thrown at src/Spectre.Console.Ansi/AnsiMarkupTagParser.cs:10

namespace Spectre.Console;

internal static class AnsiMarkupTagParser
{
    public static (Style Style, Link? Link) Parse(string text)
    {
        var result = Parse(text, out var error);
        if (error != null)
        {
            throw new InvalidOperationException(error);
        }

        return result ?? throw new InvalidOperationException("Could not parse style.");
    }

    public static bool TryParse(string text, [NotNullWhen(true)] out (Style Style, Link?)? result)
    {
        result = Parse(text, out _);
        return result != null;
    }

    private static (Style Style, Link? Link)? Parse(string text, out string? error)
    {
        var effectiveDecoration = (Decoration?)null;
        var effectiveForeground = (Color?)null;
        var effectiveBackground = (Color?)null;
        var effectiveLink = (string?)null;

View on GitHub (pinned to 0acc92fada)

Solutions

1. Provide exactly 6 hex digits (#RRGGBB) or 3 (#RGB)
2. Format integers as X6 to guarantee 6 digits, e.g. $"#{value:X6}"
3. Validate length before embedding

Example fix

// before
AnsiMarkup.Parse($"[#{value:X}]text[/]"); // X can produce fewer than 6 digits

// after
AnsiMarkup.Parse($"[#{value:X6}]text[/]");

public static bool IsValidHexLength(string token)
{
    var h = token.TrimStart('#');
    return h.Length == 3 || h.Length == 6;
}

try { AnsiMarkup.Parse(markup); }
catch (InvalidOperationException ex) when (ex.Message.StartsWith("Invalid hex color"))
{ /* pad to 6 digits with value.ToString("X6") */ }

When it happens

Trigger: A `#`-prefix with the wrong digit count: `[#1234]` (4 digits), `[#1234567]` (7 digits), `[#]` (empty), or `[#12]` (2 digits).

Common situations: Code that builds hex from a value not padded to 6 digits; stripping/trimming that shortens the string; off-by-one in substring slicing.

Related errors

• Invalid hex color '#{hex}'. {ex.Message}
• Color number must be greater than or equal to 0 (was {number
• Color number must be less than or equal to 255 (was {number}
• Could not find color '{part}'.
• Could not find color or style '{part}'.

AI-assisted analysis of spectreconsole/spectre.console@0acc92fada (2026-08-13). Data as JSON: /api/errors/8cafe2089ac736ef. Report an issue: GitHub.