Why so dark?

Why's the screen so dark?  When I first built this app I used a white background.  However, I became concerned about battery life.  Quite often it takes me a while to gather my thoughts and capture them in a succinct manner.  Having a white background displayed while I try to organize and capture my thoughts just seemed like a waste of battery time to me.  This app is designed for contemplation, not simply opening it, doing something, and closing it.  I changed the background to black and think it looks fairly clean.  I really have no idea how much battery life this may save and I'm not about to do a study on it.  However, I think for this app the black background makes sense.   So why the blue to yellow?  Do you mean blue to sunny?  Hmmmmm.