If you're using gradients within your CSS, you may have encountered an issue with colors in IE. The problem is that the filter parameters don't allow the RGB shorthand color notation like standard CSS does.
For, example, if you're using:
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#888', endColorstr='#bbb');
Internet Explorer will assume that your RGB color values are simply incomplete (as opposed to assuming that they are shorthand).
Using the full hexadecimal RGB color value will resolve the issue.
filter: progid:DXImageTransform.Microsoft.gradient(startColorstr='#888888', endColorstr='#bbbbbb');