We have implemented a mode for players that are affected by deuteranopia (red-green colorblindness) so they can better distinguish between friendly and enemy health bars as well as spell effects during gameplay.
You can see the original post about this here: http://na.leagueoflegends.com/board/showthread.php?t=1701655&highlight=colorblind+mode
How to use Colorblind Mode
While in game hit your 'Esc' key and you will pull up the options menu. Click the 'Video' tab:
Next click 'Colorblind Mode' under the Resolution:
Like all features for League of Legends, we will continue to support our colorblind modes as the game continues to evolve, so don't be surprised if you see additional options become available in future patches!