IE rules from Colibri apply to Flamingo as well at the moment. Please see attached for an issue example.
Add support for specific stylesheets for IE browsers
On Flamingo the Colibri gradients are applied since they are found in colibri/ie-all.css
<link href="/xwiki/bin/skin/skins/colibri/ie%2Dall.css?colorTheme=ColorThemes.DefaultColorTheme" rel="stylesheet" type="text/css"/>
Done in 2777425b0935434f90fd9cd9b2b1f3ec2ed5506a
Added flamingo/ie-all.css to host future IE specific rules.