I find it extremely difficult to spot the currently selected tab in Intellij, if using the Darcula theme. I've looked for a workaround and I was not able to find any solution besides disabling the "Use in Editor Tabs" checkbox in Settings->Appearance&Behavior->FileColors.
This issue has been reported by several other users (e.g. this question), but I can't seem to solve it for the current version of Intellij/Darcula.
Thanks