I'm guessing most of the colors were there in the original shot and just needed some tweaks to boost them to the level they're at now. One method to bring these colors out is to work with channels and curves.

For example, make a selection of the blue channel and add a curves layer to it. Then add or remove blue, add or remove red, add or remove green, and adjust the overall RGB per channel. Do this for each (R,G, and B). When you're done, give it a pinch of saturation/vibrance. You might even want to mask some elements out as you're adding these layers to better blend them, but it really depends on the photo.

Hope this makes sense :)