How to change the Internal Note background color?

Hi,

In certain lighting during the day or when adjusting the screen to warm colors, there is almost no difference between the light-pitch background of the internal note and the white background of the public reply (especially since the dialog is at the bottom of the screen creating a low-angle with the eye). 

It already happened a few times where we sent a private reply to a client by mistake.  

Is it possible to change the private reply background color to something more intense (or white text on a black background)?