I have been manually modifying the clrtabs.css file since 'Australis' came out, to achieve this. I comment out all the ".australis" lines (except the one with #navigator-toolbox, as it keeps the tab-color line under the tab bar), to make the selected tab highlighted (light gray curved tab). It also shows a curved tab silhouette if you mouse hover, without changing the color, which I find useful too (see attached pics). I haven't messed with the .mac.australis lines, since I don't use a Mac, so not sure what that would do.
Shivanand,
Can the 'Highlight the currently selected tab' option in Styles be used to disable those .australis parts in clrtabs.css, or something similar, to indicate the active tab? I think its property is 'tab.tabbrowser-tab.standout', related to colorfulTabs.standout and extensions.clrtabs.standout. That option currently doesn't do anything, at least on Windows and Linux; not sure about Mac. In clrtabsopt.xul:
<checkbox id="standoutcheck" preference="standout" label="Highlight the currently selected tab."/>
I tried messing with it myself with no luck, as I don't know css; such as adding this to all the .australis lines:
.australis #tabbrowser-tabs[tabsontop=true] > tab.tabbrowser-tab.standout > .tab-stack > .tab-content[selected=true],
...and various other permutations.
I've attached pics of how it looks with my manual edit, one showing just the current tab, and another including mouse hover (the mouse pointer is not captured in the screenshot).