TUTORIAL: how to boost the colors of an image
Choose an image and create a new layer. Use a soft white brush with 50% opacity to lighten up the places where you can see the lights on the pic. For example, on the cap I chose, I will use the soft brush on Blair's head, back, and the left side of Serena's face.
Now duplicate the base and put it above this layer on soft light or whatever fusion you find cool (soft light and overlay are the best, imo). You can see your pic has already lightened up a little.
Now go to Filters > Gaussian Blur > and choose a high number for the blur and apply the effect. This number up to you, you can even not blur the pic if you think it's not nice. I chose 35 as my blur output.
Create a new layer and try to cover the background and any surroundings you may want to "color" or blend or boost, to create a particular effect. Use a white soft brush with 50% opacity to do so and use the smudge tool if needed.
Click twice on this layer and exclude one of the three color channels (or two of them)
in the blending options, so that your white brush will change color. Choose the channel color you like the best, change the fusion and/or opacity if needed. You may
want to duplicate this layer as many times as you want to make it more visible.
(I duplicated mine 3 times and selected the yellow channel on some of the duplicated layers).
Another way to do this, is to use the brush on the parts of the picture you want to
enlighten: IDK, the subject has blond hair? Use the brush lightly on them
and exclude the B (blue) channel so that you'll get a yellow. Duplicate your base and put it on the top of the layers set on soft light.
TIP: the more you duplicate your base or use gaussian blur, motion blur,
or simply the blur tool, the image and the colors will deepen. Same if you
use the white soft brush on the blurred pic instead that on a new layer. You need to play around with the layers!! Different settings will give you a different outcome.
The image itself is already done at this point, but we might want to add coloring on it by using selective coloring, curves, color balance, or whatever you want to, if you'd like to boost the colors more. My advice is not too make things too confused. Do not overdo it. This type of technique needs very few enhacements. I suggest you to use just brightness/contrast or curves, or vibrance or a little selective coloring. And if you can, use gradient textures too. They will help. Textures are great to boost, you could use colorful ones and set them on overlay. You can also use the dodge and burn tool to lighten/darken parts of your base.
Last, but not last, don't forget to sharpen!
This is my result:
After the last step, I just duplicated my base, used gaussian blur and set on soft light, dragged a light blue texture set on overlay 50%, pressed CTRL + shift + ALT + E to merge all the layers and add another fuchsia texture set on screen 25%, and duplicated my merged layers and put on the top of this textures set on soft light 60%.