Lemons are just another color morph of the red tiger Oscar. Same thing with white Oscars, black Oscars, zebra Oscars and albino/lutino Oscars. All of them are just color morphs of one specie. Lemon Oscars are just one of the newest morphs out on the market. They were just selectively bred for lighter and lighter coloration over time. They can start out yellow and slowly turn a light golden orange color over time as they mature. Some will keep the yellow lemon colour.