fixing potential 7 char hex color causing issue

[YuDavidCao]

Checklist

• yarn typecheck
• yarn lint:fix
• yarn test
• yarn brl
• yarn changeset
• ui changelog

If the opacity is set to a low value the original code will generate 7 character hex color.

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Project	Deployment	Preview	Comments	Updated (UTC)
plate	Ready	Preview	Comment	Oct 26, 2025 5:15pm