i wont go into detail of how to change the header and such but i will tell you all, daisy and others maybe you can make this core change. 

i found out if you change this css

div.ow_chat_dialog.ow_chat_new_message

give it a background-color and a height of 2px, then when someone sends you a PM the whole head box will blink rather than just the bottom border when you get a message.

I have noticed also that there are alot of css background statements that prob need to be changed to background-color: in stead.

Thanks for the reply Daisy, yeah my members love the new blink header and its not just the header, if you have it mimimized its just the header which is cool, but also if you have it open but your not focus on it, the whole thing blinks and they love it, and then all you have to do is focus on it and it stops blinking.

Thanks so much enjoy your day :)

Could you share the modifications you did so that both the personal box and the main box blink whenever new messages are received?  I would like them to blink if they are fully open or minimized...

Thank you very much!

But isn't there anything that could be done to make the main box blink, too?

By default, the notification displayed by the main box is far too easy to miss!

What could be done to achieve that?

Thank you very much!

Is yours yellow, i think its yellow by default i dont remember, if not then you can change the color to yellow, if it is yellow then youll have to see how much a developer would charge you to make it blink or you could mod it yourself but remember when there is an update you will lose that mod. 

This is what I get when a new IM comes in:

Number "1" goes from gray to orange...

This is default behaviour with the Origin theme.

Are you getting something more noticeable from other themes?

Thanks!