Please, could you be more specific on this.
I suppose it works like this:
When the call is answered taskbar icon should blink with a very slow rate (slower than when showing notification on incoming call) until you press mouse somewhere in it's window.
This will happen when you answer from a headset or from a phone in CTI mode.
I know that's not very good. We should stop blinking somehow, but this is how Windows works.
According to Windows the point of the flashing is to get the user's attention. The button stays coloured because the user still may not have looked down and discovered which window was trying to get her attention. Keeping the button coloured keeps that information available.
Now i'm thinking of a user option to enable/disable blinking feature. Cause if you're on CTI or using a headset that can annoy.