Add this to an addon:
Code:
CHAT_FRAME_TAB_SELECTED_MOUSEOVER_ALPHA = 1
CHAT_FRAME_TAB_SELECTED_NOMOUSE_ALPHA = 0
CHAT_FRAME_TAB_ALERTING_MOUSEOVER_ALPHA = 0
CHAT_FRAME_TAB_ALERTING_NOMOUSE_ALPHA = 0
CHAT_FRAME_TAB_NORMAL_MOUSEOVER_ALPHA = 1
CHAT_FRAME_TAB_NORMAL_NOMOUSE_ALPHA = 0