title: How to change the colours of the background of the screen in kivy app module of python?
body: <p>I have a developed kivy app in python but I have an issue: Sometimes the black background is too dark and I wonder if it's possible that in Kivy the attribute <code>Screen</code> has a property that could change to negative colours, I mean, like some mobile phones that you can choose to change all the colours of the mobile to negative, solving the problem of the colours. I'm new about developing with Kivy, so I don't know about the potentiality of Kivy about solving this problem. I've been looking for a few days and I haven't found out anything. If someone knows how to fix this incovenience it would be very helpful. </p>