The 'color' field contains a number, single character, abbreviation, or non-color value. Use real color names and slash-delimit blends (e.g., 'red/blue').
Microsoft Merchant Center's product schema has format and value rules per attribute. This issue is typically: missing a required attribute for the category, an invalid enum value (e.g., 'XL' submitted where 'M, L, XL' is the valid set), out-of-range numbers, or attributes that conflict across the feed.