Cannot Highlight current tab SeaMonkey 2.0.3

Try to disable Coral IE Tab. Please also send a screenshot.

Are you trying to highlight by setting the "Fading Level" or by using the checkbox "Highlight the currently selected tab"?

You are using the "Modern" Theme which limits the effect of this settings. The checkbox "Highlight the currently selected tab" changes the background image of the selected tab to give a concave effect as against the convex effect of the other tabs. You can try toggling this setting again to notice the difference. This effect is more pronounced in the default theme.

I'm not sure where the red square with a white X come in. ColorfulTabs doesn't do anything with them. In Firefox and Seamonkey, the highlighting is done via background effect. Additionally we provide the fading function.

This is the colorful tab and the one with the red square and white x is the selected
tab. Where did it come from if not from colorful tabs?

I see what you mean.
With CorfulTabs disabled, it still appears so it must be in the Firefox Browser and
it's not in SeaMonkey.

All along, I thought it was part of ColorfulTabs.

Thanks for the help.