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Link to issue

Closes #5867

Description of change

The color validator now accepts the CSS color syntax that plotly.js parses: signed and exponent numbers, angle units other than deg, the none keyword, any color() color space, and transparent. Before, values like lab(50% -40 59.5) or color(srgb 1 0 0) raised a ValueError even though plotly.js renders them.

Demo

import plotly.graph_objects as go

go.Scatter(marker_color="lab(50% -40 59.5)")
# before: ValueError: Invalid value of type 'builtins.str' received for the 'color' property of scatter.marker
# after: accepted

Testing strategy

Added valid and invalid cases to test_color_validator.py. I checked each of them against culori, the parser plotly.js uses, so the validator accepts and rejects the same strings.

Additional information (optional)

The old code removed spaces before matching so the regex didn't have to handle them. The new regex handles whitespace itself, so that step is gone. Strings that don't form a valid color function, like rgb(255, 0) or rgb(1-2 3 4), are still rejected.

Guidelines

• I have reviewed the pull request guidelines and the Code of Conduct and confirm that this PR follows them.
• I have added an entry to the changelog if needed (not required for documentation PRs).