Letham is an anagram of the word "Hamlet" which is referred to numerous times throughout the film.
The color yellow is used prominently throughout the film. It represents sunshine, happiness, loyalty, joy, optimism, remembrance and warmth. It energizes mood and relieves depression. It's the lightest and brightest color on the color wheel. It's an attention getter - one reason taxi caps are painted yellow and in most countries traffic lights and signs are yellow, meaning caution. Even some blind people can detect the color yellow. On the other hand, it represents cowardice and deceit. Judas is often depicted wearing yellow.
Massive Attack's song "Angel" is prominently featured on in Doug Liman's Go (1999) and Marc Forster's Stay (2005) - movies with opposing titles.