I have a main activity where users can change (via preferences) the background colour to their favourite colour. My problem is that I can not change the background colour o
I kinda faced the same problem. And the only way to solve it was extending my own version of layout. I see that in your case it is an AlertDialog. What I recommend you to do, is to create a unique class, that is your customized AlertDialog and create a layout for this, and then you inflate this.
Here is a post that helped me a lot. http://blog.androgames.net/10/custom-android-dialog/
I followed this post and solved my problem with customizing dialogs.
Please, if you have more doubts, let me know.
Thanks.