Q: MagSafe charger randomly changing color from orange to green and back.

There may be some relevant information about some of the possible

causes of the symptoms your MacSafe charger & MacBook, here:

•Apple Portables: Troubleshooting MagSafe adapters - Apple Support

To wait or delay the recharge of this type of battery until it is near flat

or dead status, could be damaging or bad for the cells within it. You

cannot always count on the percentage indicator to tell you accurate

information on exact power reserves; so be sure to avoid totally

running out of battery power or close-calls that run it near flat.

•Mac notebooks: All about batteries - Apple Support

http://www.apple.com/batteries/maximizing-performance/

While the advice to check the tiny connection pins in the power plug,

there also may be a need to have the computer & magsafe, plus the

battery and maybe the MagSafe Board (DC in-board) tested at an

authorized Apple service, or maybe checked at Apple Store, Genius.

Good luck & happy computing!