I'm always incorporating color meaning into symbolic interpretations. As with anything, color adds an extra layer of depth, quality and meaning to the overall view. When colors are shown to me, I typically revert to the chakras for intuitive cues. The chakras can serve as effective blueprint for color meaning.
A back-end application or program serves indirectly in support of the front-end services, usually by being closer to the required resource or having the capability to communicate with the required resource.
PHP is server-side. Basically, Angular handles all the viewing etc inside the browser and on the same page, sending requests to the backend API (e.g created via PHP) to handle database requests and so forth. Angular and PHP serves two completely different functions and can be used together, not in place of one another.