- An HTML element must be using the deprecated bgcolor attribute. This will likely be a table, tr, or td element.
- The color must be specified using the hexadecimal short notation, i.e. #123 instead of #112233
Internet Explorer cannot read short-notation hexadecimal colors in this particular property. It will instead improvise by applying a background color of black.
The simple solution is to not use the bgcolor attribute, but if you have no control over the markup, use a full-length hexadecimal value instead. If you're working in an application where you have no control over the markup or the value of this property but can apply CSS with a style sheet, slap the developers in the face and attempt to target the elements to override the color. Don't try to use attribute selectors though (see here for more information).