tui-cs/Terminal.Gui · error · FormatException

Failed to parse Color from {s}

Error message

Failed to parse Color from {s}

What it means

This error is thrown by FileSystemColorProvider.StringToColor() when Color.TryParse fails to parse a string into a Color value. The FileSystemColorProvider maps file names and extensions to colors for display in file dialogs. If a color string in the configuration (FilenameToColor or ExtensionToColor dictionaries) is not a valid color representation, a FormatException is thrown with the offending string.

Source

Thrown at Terminal.Gui/FileServices/FileSystemColorProvider.cs:451

            return extColor;
        }

        return null;
    }

    private static Color StringToColor (string str)
    {
        if (!Color.TryParse (str, out Color? c))
        {
            ThrowFormatException (str);
        }

        return c.Value;

        [DoesNotReturn]
        static void ThrowFormatException (string s)
        {
            throw new FormatException ($"Failed to parse Color from {s}");
        }
    }
}

View on GitHub (pinned to 2e47b11478)

Solutions

1. Verify the color string against Terminal.Gui's supported color names (e.g., 'red', 'blue', 'green') and valid hex formats ('#RRGGBB').
2. Use Color.TryParse yourself before adding to the dictionary to get a clear failure point.
3. Check the config file or code that populates FileSystemColorProvider for typos.
4. Correct the invalid color string to a valid color name or hex value.

Example fix

// before -- invalid color string causes FormatException
provider.FilenameToColor["file.txt"] = FileSystemColorProvider.StringToColor("bluw");

// after -- validate before use
if (Color.TryParse("blue", out Color? c)) { provider.FilenameToColor["file.txt"] = c.Value; }

string colorStr = "blue";
if (Color.TryParse(colorStr, out Color? c)) { provider.FilenameToColor["file.txt"] = c.Value; }
else { Console.Error.WriteLine($"Invalid color: {colorStr}"); }

try { Color color = StringToColor(colorStr); }
catch (FormatException ex) { Console.Error.WriteLine($"Bad color config: {ex.Message}"); /* use default color */ }

When it happens

Trigger: Thrown at FileSystemColorProvider.cs:451 (inside ThrowFormatException, called from StringToColor at line 443) when Color.TryParse(str, out Color? c) returns false. StringToColor is used internally when populating the FilenameToColor and ExtensionToColor dictionaries. The trigger is an invalid color string being added via configuration or code.

Common situations: A typo in a color configuration string (e.g., 'bluw' instead of 'blue'), using a color name not recognized by the Color parser (e.g., a CSS color name not in Terminal.Gui's color set), providing an invalid hex format (e.g., '#GGGGGG'), or loading a config file with corrupt color values.

Understand the failure class

• Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

• Unexpected color name: {colorString}.
• Unexpected token when parsing Color: {reader.TokenType}
• Provided text is too short to be any known color format.
• The text provided was null or empty.
• The text provided consisted of only whitespace characters.

AI-assisted analysis of tui-cs/Terminal.Gui@2e47b11478 (2026-08-13). Data as JSON: /api/errors/5818857015ac6fb1. Report an issue: GitHub.