In my hacked .css, the part that is commented out can be shortened back to here without noticeable impact (tested in Win7/8/10 and Linux):
.australis .tabbrowser-tab .tab-background-middle,
.australis .tabbrowser-tab:hover .tab-background {
background-image:none !important;
background-color:transparent !important;
} */
Or another interesting option, if its moved back one more section, it will still show part of the original color, to allow reference to other domains (if using the domain coloring option, as I do); like this:
.australis .tabbrowser-tab .tab-background {
margin-left:0;
margin-right:0;
} */
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Note, that my previously attached .css doesn't have your latest merge for 'max-width' in that file (which I put in my own .css):
.colorfultabs-minified tab:not([pinned]) {
min-width:32px;
max-width:48px;
margin-left:10px;
}
.colorfultabs-minified tab:not([pinned])[selected="true"] {
min-width:48px;
max-width:64px;
}