This tall light green grass growing with the bermuda

It would help if you said where you are. However, if you're in the southern US, Saint Augustine would be a good choice. If you're in a cooler climate some types of Fescue might work for you. Another thing to consider would be a ground cover - perhaps Jasmine.

I've heard of using asphalt shingles as a barrier between grass and flower beds (just dig a trench and bury a line of shingles, may not be pretty but it's effective) and that should stop any more grass from spreading but as for the existing grass you may be forced to either use RoundUp or chop it out and re-seed. I'm not sure of any chemical or other control method that targets Bermuda grass specifically.