In theory, themes with darker backgrounds should affect battery life a little more than themes with whiter/lighter colors due to the nature of the LCD panel.
Don't know if enough to make a significant noticeable difference dough.
Off course almost all themes reduce battery life. I am not talking about system themes but others. I noticed it on almost all android devices i have held....
Could someone else test something out for me just to make sure it isn't just me or my imagination? I've noticed for some reason whenever I use the default font that comes with the phone. My phone's battery life improves. Does anyone else notice this?