Currently there is a green glow outline on the turn button when the game thinks you've finished doing everything (all units have moved or passed, no city queues empty, that kind of thing).

My problem with the green glow thing.  It pulses tooooooo slow.  I think it used to pulse faster.  Now I kind of wait for 10-20 seconds to make sure it isn't in its non-glow pulse state, or in that time it will slowly glam it up to a green colour.

My solution: Make the pulse cycle shorter.  The effect is good.  Just the pulse cycle is tooooooooo slow.  The pulse cycle could be something more like 5 seconds.  Which means even if you look at the button in its down stat, no more than 1 second will pass before you can see some more green happening

Second Solution (not by The Living End): Have a permanent effect/diffferent artwork on the turn button when the game thinks you're ready to finish the turn.