EN-GB locale number formatting

This issue happens because Excel’s number format parser changes slightly depending on the language and regional settings. In the English (UK) locale, Excel expects “Colour” instead of “Color,” which causes your format string to break even though it follows the OpenXML standard. Unfortunately, Excel’s behavior here isn’t consistent across locales, it’s more of a legacy quirk than an intentional feature. The best way to keep your formatting portable is to use numeric color codes (like [Color1] through [Color56]) instead of color names or any localized spelling. This approach works across all Excel languages and avoids problems when a workbook generated on a server is opened in a different regional version.

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