Question
I have a tiff green bermuda lawn.  How do I get it to be a deep dark green color?  

Answer
paint it dark green...just kidding
depends on where you live. i'm in southern NJ. we have cool weather grasses here. yours is a warm weather grass grown in more temperate climates. fertilizing at the right time and with the right product would help. get to a local garden center/nursery and quiz them on a solution to your problem. buy your products from them and they should be more than happy to help you.