I am wanting a Malawi African Cichlid tank but, I don't know what are some good one's to add with Yellow labs. Anyone able to give me a clue on what I should add in with them to get very colorful fish in the tank.
I recommend looking through the articles in the forum library here for things to learn about African cichlids before choosing. There are items like a chart of how aggresive you might expect each type to be. I would look that over and choose from some of the ones less likely to give you trouble. A good way to get some good experience rather than buying trouble right off the bat.
You can mix Herbevoures and Carnivours, you just have to use a compatible food. Use foods that have a mix of protein and plant matter. NLS, Omega 1, are popular, there are others. Main problems of mixing Cichlids is different aggresion levels and possibility of cross breeding. (No two types of the same speices)
Perhaps read the cookie cutter section of the library as mentioned above.
Often things are overstated. There are "tendancies" which sometimes get thought of as rules. For cross breeding I find it works out like this. If there are males and females and each of several types has enough females of his type, he hits on them. If there are no females of his type, he may hit on other types. Think of it as a bar. If there are girls there of your favorite type, you go for them. If not, you may try for anything there! Simgle male fish act like single male people. If there are fish there of a different type but look a lot like his type, he is more likely to go for it. Simple when you think about it?
For food, I just try to feed a general food and vary it with other types. Flakes, pellets, and algea tablets. If I have algea eating types only I avoid feeding too much protein to avoid causing Malawi bloat.
If you don't plan on raising fry, crossbreeding is not such a huge issue. And I agree with PfunMo, it may not necessarily happen, even if you do have fish of the same genus. I successfully had Cobalt blue zebras and Red zebras in the same tank and they did not crossbreed. I did have proper M/F ratios of both.
With a 125g tank, you could easily have 6-8 types of Mbuna, depending on size/aggression. Look in the profiles section and see which fish you like. The main thing to keep in mind is that similar colors may cause more aggression, and it's usually best to just keep one type of barred fish (for example, don't mix Ps. Demasoni with Ps. Saulosi, because they both have blue barred varieties.)